Salen complexes with dianionic counterions

ABSTRACT

The present invention describes metal salen complexes having dianionic counterions. Such complexes can be readily precipitated and provide an economical method for the purification and isolation of the complexes, and are useful to prepare novel polymer compositions.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. national phase application under 35U.S.C. §371 of International Application No. PCT/US2012/068985, filedDec. 11, 2012, which claims priority to U.S. provisional applicationSer. No. 61/569,286 filed Dec. 11, 2011, and to U.S. provisionalapplication ser. No. 61/570,974 filed Dec. 15, 2011; the entire contentsof each of which are hereby incorporated herein by reference.

GOVERNMENT SUPPORT

The invention was made in part with United States Government supportunder grants DE-FE0002474 awarded by the Department of Energy. TheUnited States Government has certain rights in the invention.

FIELD OF THE INVENTION

The invention pertains to the field of chemical synthesis. Moreparticularly, the invention pertains to metal salen complexes with acounterion selected to allow isolation and purification of suchcomplexes by precipitation.

BACKGROUND

Members of the class of ligands made by condensation of a diamine withtwo molar equivalents of optionally functionalized salicylaldehydemolecules are commonly referred to as salen ligands or “salens” afterthe simplest member of the class, N,N′-ethylenebis(salicylimine). Thesalen ligand may be either symmetric (containing two identicaloptionally functionalized salicylaldehyde moieties) or non-symmetric(containing two different optionally functionalized salicylaldehydemoieties).

This class of ligands may be generalized further to include compoundsformed by condensation of a diamine with two molar equivalents ofoptionally functionalized β-hydroxy carbonyl compounds. As notedearlier, the ligands may be either symmetric or non-symmetric. Thesetetradentate ligands form Co(III) and Cr(III) complexes when the twooxygen atoms and the two nitrogen atoms of the ligand form bonds withmetal atom. The remaining +1 charge on the metal is balanced by ananionic counterion. Cr(III) and Co(III) salen complexes have been shownto catalyze epoxide hydrolysis, epoxide-CO₂ copolymerization, and phenoloxidation, among other reactions. In some cases, isolation of thedesired salen complexes comprising monoanionic counterions (nitrate,chloride, acetate, trifluoroacetate, and other monocarboxylic acids forexample) is difficult owing to poor precipitation. Often, when attemptsare made to precipitate such compounds, a viscous oil or sticky solidthat cannot be easily handled until exhaustively dried is formed. Thisis not an efficient or economical method for isolation on manufacturingscale; furthermore, isolation in this manner does not provide any meansfor purification, which is desirable for a catalytic species.Alternatively, it would be desirable to precipitate a Cr(III) or Co(III)salen complex directly from a crude reaction mixture by the addition ofa co-solvent or the removal of a solvent which dissolves the complex.

SUMMARY OF THE INVENTION

The present invention encompasses the recognition that dianioniccounterions in Cr(III) and Co(III) salen complexes can allow efficientprecipitation of the complexes from solution and thereby provide aneffective means for the convenient isolation and purification of thesalen complexes. The present invention provides, among other things,such Cr(III) and Co(III) salen complexes with dianionic counterions. Thepresent invention also provides solvent systems useful for theprecipitation of the metal salen complexes containing dianioniccounterions as well as methods for purifying the complexes.

In certain embodiments, provided compounds are of Formula I:

Wherein, R^(1a), R^(2a), R^(3a), R^(1a′), R^(2a′), R^(3a′), R^(J),R^(G), M and δ are as defined below and in the specific embodiments andexamples herein.

In certain embodiments, the present invention also provides methods forthe purification of metal salen complexes. Such methods include a stepof converting the metal salen complex to a compound having a dianioniccounterion and then precipitating the complex.

In certain embodiments, the present invention provides novel aliphaticpolycarbonate compositions characterized in that they have a unimodalmolecular weight distribution.

DEFINITIONS

Definitions of specific functional groups and chemical terms aredescribed in more detail below. For purposes of this invention, thechemical elements are identified in accordance with the Periodic Tableof the Elements, CAS version, Handbook of Chemistry and Physics, 75^(th)Ed., inside cover, and specific functional groups are generally Edefined as described therein. Additionally, general principles oforganic chemistry, as well as specific functional moieties andreactivity, are described in Organic Chemistry, Thomas Sorrell,University Science Books, Sausalito, 1999; Smith and March March'sAdvanced Organic Chemistry, 5^(th) Edition, John Wiley & Sons, Inc., NewYork, 2001; Larock, Comprehensive Organic Transformations, VCHPublishers, Inc., New York, 1989; Carruthers, Some Modern Methods ofOrganic Synthesis, 3^(rd) Edition, Cambridge University Press,Cambridge, 1987; the entire contents of each of which are incorporatedherein by reference.

Certain compounds of the present invention can comprise one or moreasymmetric centers, and thus can exist in various stereoisomeric forms,e.g., enantiomers and/or diastereomers. Thus, inventive compounds andcompositions thereof may be in the form of an individual enantiomer,diastereomer or geometric isomer, or may be in the form of a mixture ofstereoisomers. In certain embodiments, the compounds of the inventionare enantiopure compounds. In certain embodiments, mixtures ofenantiomers or diastereomers are provided.

Furthermore, certain compounds, as described herein may have one or moredouble bonds that can exist as either the Z or E isomer, unlessotherwise indicated. The invention additionally encompasses thecompounds as individual isomers substantially free of other isomers andalternatively, as mixtures of various isomers, e.g., racemic mixtures ofenantiomers.

As used herein, the term “isomers” includes any and all geometricisomers and stereoisomers—both those arising from connectivity amongcarbon atoms and those arising from arrangement of coordinatingheteroatoms around chromium. For example, “isomers” include cis- andtrans-isomers, E- and Z-isomers, R- and S-enantiomers, diastereomers,(D)-isomers, (L)-isomers, racemic mixtures thereof, and other mixturesthereof, as falling within the scope of the invention. For instance, astereoisomer may, in some embodiments, be provided substantially free ofone or more corresponding stereoisomers, and may also be referred to as“stereochemically enriched.”

Where a particular enantiomer is preferred, it may, in some embodimentsbe provided substantially free of the opposite enantiomer, and may alsobe referred to as “optically enriched.” “Optically enriched,” as usedherein, means that the compound is made up of a significantly greaterproportion of one enantiomer. In certain embodiments the compound ismade up of at least about 90% by weight of an enantiomer. In otherembodiments the compound is made up of at least about 95%, 98%, 99%,99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or 99.99% by weight of an enantiomer.Enantiomers may be isolated from racemic mixtures by any method known tothose skilled in the art, including chiral high pressure liquidchromatography (HPLC) and the formation and crystallization of chiralsalts or prepared by asymmetric syntheses. See, for example, Jacques, etal., Enantiomers, Racemates and Resolutions (Wiley Interscience, NewYork, 1981); Wilen, S. H., et al., Tetrahedron 33:2725 (1977); Eliel, E.L. Stereochemistry of Carbon Compounds (McGraw-Hill, NY, 1962); Wilen,S. H. Tables of Resolving Agents and Optical Resolutions p. 268 (E. L.Eliel, Ed., Univ. of Notre Dame Press, Notre Dame, Ind. 1972).

When substituents are described herein, the term “radical” or“optionally substituted radical” is sometimes used. In this context,“radical” means a moiety or functional group having an availableposition for attachment to the structure on which the substituent isbound. In general, the point of attachment would bear a hydrogen atom ifthe substituent were an independent neutral molecule rather than asubstituent. The terms “radical” or “optionally-substituted radical” inthis context are thus interchangeable with “group” or“optionally-substituted group”.

The terms “halo” and “halogen” as used herein refer to an atom selectedfrom fluorine (fluoro, —F), chlorine (chloro, —Cl), bromine (bromo,—Br), and iodine (iodo, —I).

The term “aliphatic” or “aliphatic group”, as used herein, denotes ahydrocarbon moiety that may be straight-chain (i.e., unbranched),branched, or cyclic (including fused, bridging, and spiro-fusedpolycyclic) and may be completely saturated or may contain one or moreunits of unsaturation, but which is not aromatic. Unless otherwisespecified, aliphatic groups contain 1-30 carbon atoms. In certainembodiments, aliphatic groups contain 1-12 carbon atoms. In certainembodiments, aliphatic groups contain 1-8 carbon atoms. In certainembodiments, aliphatic groups contain 1-6 carbon atoms. In someembodiments, aliphatic groups contain 1-5 carbon atoms. In someembodiments, aliphatic groups contain 1-4 carbon atoms. In someembodiments, aliphatic groups contain 1-3 carbon atoms. In someembodiments, aliphatic groups contain 1-2 carbon atoms. Suitablealiphatic groups include, but are not limited to, linear or branched,alkyl, alkenyl, and alkynyl groups, and hybrids thereof such as(cycloalkyl)alkyl, (cycloalkenyl)alkyl or (cycloalkyl)alkenyl.

The term “unsaturated”, as used herein, means that a moiety has one ormore double or triple bonds.

The terms “cycloaliphatic”, “carbocycle”, or “carbocyclic”, used aloneor as part of a larger moiety, refer to a saturated or partiallyunsaturated cyclic aliphatic monocyclic or bicyclic ring systems, asdescribed herein, having from 3 to 12 members, wherein the aliphaticring system is optionally substituted as defined above and describedherein. Cycloaliphatic groups include, without limitation, cyclopropyl,cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl,cycloheptyl, cycloheptenyl, cyclooctyl, cyclooctenyl, andcyclooctadienyl. In some embodiments, the cycloalkyl has 3-6 carbons.The terms “cycloaliphatic”, “carbocycle” or “carbocyclic” also includealiphatic rings that are fused to one or more aromatic or nonaromaticrings, such as decahydronaphthyl or tetrahydronaphthyl, where theradical or point of attachment is on the aliphatic ring. In certainembodiments, the term “3- to 8-membered carbocycle” refers to a 3- to8-membered saturated or partially unsaturated monocyclic carbocyclicring. In certain embodiments, the terms “3- to 14-membered carbocycle”and “C₃₋₁₄ carbocycle” refer to a 3- to 8-membered saturated orpartially unsaturated monocyclic carbocyclic ring, or a 7- to14-membered saturated or partially unsaturated polycyclic carbocyclicring. In certain embodiments, the term “C₃₋₂₀ carbocycle” refers to a 3-to 8-membered saturated or partially unsaturated monocyclic carbocyclicring, or a 7- to 20-membered saturated or partially unsaturatedpolycyclic carbocyclic ring.

The term “alkyl,” as used herein, refers to saturated, straight- orbranched-chain hydrocarbon radicals derived from an aliphatic moietycontaining between one and six carbon atoms by removal of a singlehydrogen atom. Unless otherwise specified, alkyl groups contain 1-12carbon atoms. In certain embodiments, alkyl groups contain 1-8 carbonatoms. In certain embodiments, alkyl groups contain 1-6 carbon atoms. Insome embodiments, alkyl groups contain 1-5 carbon atoms. In someembodiments, alkyl groups contain 1-4 carbon atoms. In certainembodiments, alkyl groups contain 1-3 carbon atoms. In some embodiments,alkyl groups contain 1-2 carbon atoms. Examples of alkyl radicalsinclude, but are not limited to, methyl, ethyl, n-propyl, isopropyl,n-butyl, iso-butyl, sec-butyl, sec-pentyl, iso-pentyl, tert-butyl,n-pentyl, neopentyl, n-hexyl, sec-hexyl, n-heptyl, n-octyl, n-decyl,n-undecyl, dodecyl, and the like.

The term “alkenyl,” as used herein, denotes a monovalent group derivedfrom a straight- or branched-chain aliphatic moiety having at least onecarbon-carbon double bond by the removal of a single hydrogen atom.Unless otherwise specified, alkenyl groups contain 2-12 carbon atoms. Incertain embodiments, alkenyl groups contain 2-8 carbon atoms. In certainembodiments, alkenyl groups contain 2-6 carbon atoms. In someembodiments, alkenyl groups contain 2-5 carbon atoms. In someembodiments, alkenyl groups contain 2-4 carbon atoms. In someembodiments, alkenyl groups contain 2-3 carbon atoms. In someembodiments, alkenyl groups contain 2 carbon atoms. Alkenyl groupsinclude, for example, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl,and the like.

The term “alkynyl,” as used herein, refers to a monovalent group derivedfrom a straight- or branched-chain aliphatic moiety having at least onecarbon-carbon triple bond by the removal of a single hydrogen atom.Unless otherwise specified, alkynyl groups contain 2-12 carbon atoms. Incertain embodiments, alkynyl groups contain 2-8 carbon atoms. In certainembodiments, alkynyl groups contain 2-6 carbon atoms. In someembodiments, alkynyl groups contain 2-5 carbon atoms. In someembodiments, alkynyl groups contain 2-4 carbon atoms. In someembodiments, alkynyl groups contain 2-3 carbon atoms. In someembodiments, alkynyl groups contain 2 carbon atoms. Representativealkynyl groups include, but are not limited to, ethynyl, 2-propynyl(propargyl), 1-propynyl, and the like.

The term “aryl” used alone or as part of a larger moiety as in“aralkyl”, “aralkoxy”, or “aryloxyalkyl”, refers to monocyclic andpolycyclic ring systems having a total of five to 20 ring members,wherein at least one ring in the system is aromatic and wherein eachring in the system contains three to twelve ring members. The term“aryl” may be used interchangeably with the term “aryl ring”. In certainembodiments of the present invention, “aryl” refers to an aromatic ringsystem which includes, but is not limited to, phenyl, biphenyl,naphthyl, anthracyl and the like, which may bear one or moresubstituents. Also included within the scope of the term “aryl”, as itis used herein, is a group in which an aromatic ring is fused to one ormore additional rings, such as benzofuranyl, indanyl, phthalimidyl,naphthimidyl, phenantriidinyl, or tetrahydronaphthyl, and the like. Incertain embodiments, the terms “6- to 10-membered aryl” and “C₆₋₁₀ aryl”refer to a phenyl or an 8- to 10-membered polycyclic aryl ring. Incertain embodiments, the term “6- to 12-membered aryl” refers to aphenyl or an 8- to 12-membered polycyclic aryl ring. In certainembodiments, the term “C₆₋₁₄ aryl” refers to a phenyl or an 8- to14-membered polycyclic aryl ring.

The terms “heteroaryl” and “heteroar-”, used alone or as part of alarger moiety, e.g., “heteroaralkyl”, or “heteroaralkoxy”, refer togroups having 5 to 14 ring atoms, preferably 5, 6, or 9 ring atoms;having 6, 10, or 14 it electrons shared in a cyclic array; and having,in addition to carbon atoms, from one to five heteroatoms. The term“heteroatom” refers to nitrogen, oxygen, or sulfur, and includes anyoxidized form of nitrogen or sulfur, and any quaternized form of a basicnitrogen. Heteroaryl groups include, without limitation, thienyl,furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl,oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl,thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl,purinyl, naphthyridinyl, benzofuranyl and pteridinyl. The terms“heteroaryl” and “heteroar-”, as used herein, also include groups inwhich a heteroaromatic ring is fused to one or more aryl,cycloaliphatic, or heterocyclyl rings, where the radical or point ofattachment is on the heteroaromatic ring. Nonlimiting examples includeindolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl,indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl,cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl,carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl,tetrahydroquinolinyl, tetrahydroisoquinolinyl, andpyrido[2,3-b]-1,4-oxazin-3(4H)-one. A heteroaryl group may be mono- orbicyclic. The term “heteroaryl” may be used interchangeably with theterms “heteroaryl ring”, “heteroaryl group”, or “heteroaromatic”, any ofwhich terms include rings that are optionally substituted. The term“heteroaralkyl” refers to an alkyl group substituted by a heteroaryl,wherein the alkyl and heteroaryl portions independently are optionallysubstituted. In certain embodiments, the term “5- to 10-memberedheteroaryl” refers to a 5- to 6-membered heteroaryl ring having 1 to 3heteroatoms independently selected from nitrogen, oxygen, or sulfur, oran 8- to 10-membered bicyclic heteroaryl ring having 1 to 4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur. In certainembodiments, the term “5- to 12-membered heteroaryl” refers to a 5- to6-membered heteroaryl ring having 1 to 3 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, or an 8- to 12-memberedbicyclic heteroaryl ring having 1 to 4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur.

As used herein, the terms “heterocycle”, “heterocyclyl”, “heterocyclicradical”, and “heterocyclic ring” are used interchangeably and refer toa stable 5- to 7-membered monocyclic or 7- to 14-membered bicyclicheterocyclic moiety that is either saturated or partially unsaturated,and having, in addition to carbon atoms, one or more, preferably one tofour, heteroatoms, as defined above. When used in reference to a ringatom of a heterocycle, the term “nitrogen” includes a substitutednitrogen. As an example, in a saturated or partially unsaturated ringhaving 0-3 heteroatoms selected from oxygen, sulfur or nitrogen, thenitrogen may be N (as in 3,4-dihydro-2H-pyrrolyl), NH (as inpyrrolidinyl), or ⁺NR (as in N-substituted pyrrolidinyl). In someembodiments, the term “3- to 7-membered heterocyclic” refers to a 3- to7-membered saturated or partially unsaturated monocyclic heterocyclicring having 1 to 2 heteroatoms independently selected from nitrogen,oxygen, or sulfur. In some embodiments, the term “3- to 8-memberedheterocycle” refers to a 3- to 8-membered saturated or partiallyunsaturated monocyclic heterocyclic ring having 1 to 2 heteroatomsindependently selected from nitrogen, oxygen, or sulfur. In someembodiments, the term “3- to 12-membered heterocyclic” refers to a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1 to 2 heteroatoms independently selected from nitrogen,oxygen, or sulfur, or a 7- to 12-membered saturated or partiallyunsaturated polycyclic heterocyclic ring having 1-3 heteroatomsindependently selected from nitrogen, oxygen, or sulfur. In someembodiments, the term “3- to 14-membered heterocycle” refers to a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1 to 2 heteroatoms independently selected from nitrogen,oxygen, or sulfur, or a 7- to 14-membered saturated or partiallyunsaturated polycyclic heterocyclic ring having 1-3 heteroatomsindependently selected from nitrogen, oxygen, or sulfur.

A heterocyclic ring can be attached to its pendant group at anyheteroatom or carbon atom that results in a stable structure and any ofthe ring atoms can be optionally substituted. Examples of such saturatedor partially unsaturated heterocyclic radicals include, withoutlimitation, tetrahydrofuranyl, tetrahydrothienyl, pyrrolidinyl,pyrrolidonyl, piperidinyl, pyrrolinyl, tetrahydroquinolinyl,tetrahydroisoquinolinyl, decahydroquinolinyl, oxazolidinyl, piperazinyl,dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl,and quinuclidinyl. The terms “heterocycle”, “heterocyclyl”,“heterocyclyl ring”, “heterocyclic group”, “heterocyclic moiety”, and“heterocyclic radical”, are used interchangeably herein, and alsoinclude groups in which a heterocyclyl ring is fused to one or morearyl, heteroaryl, or cycloaliphatic rings, such as indolinyl,3H-indolyl, chromanyl, phenanthridinyl, or tetrahydroquinolinyl, wherethe radical or point of attachment is on the heterocyclyl ring. Aheterocyclyl group may be mono- or bicyclic. The term“heterocyclylalkyl” refers to an alkyl group substituted by aheterocyclyl, wherein the alkyl and heterocyclyl portions independentlyare optionally substituted.

As used herein, the term “partially unsaturated” refers to a ring moietythat includes at least one double or triple bond. The term “partiallyunsaturated” is intended to encompass rings having multiple sites ofunsaturation, but is not intended to include aryl or heteroarylmoieties, as herein defined.

One of ordinary skill in the art will appreciate that the syntheticmethods, as described herein, may utilize a variety of protectinggroups. By the term “protecting group,” as used herein, it is meant thata particular functional moiety, e.g., O, S, or N, is masked or blocked,permitting, if desired, a reaction to be carried out selectively atanother reactive site in a multifunctional compound. In someembodiments, a protecting group reacts selectively in good yield to givea protected substrate that is stable to the projected reactions; theprotecting group is preferably selectively removable by readilyavailable, preferably non-toxic reagents that do not attack the otherfunctional groups; the protecting group forms a separable derivative(more preferably without the generation of new stereogenic centers); andthe protecting group will preferably have a minimum of additionalfunctionality to avoid further sites of reaction. By way of non-limitingexample, hydroxyl protecting groups include methyl, methoxylmethyl(MOM), methylthiomethyl (MTM), t-butylthiomethyl,(phenyldimethylsilyl)methoxymethyl (SMOM), benzyloxymethyl (BOM),p-methoxybenzyloxymethyl (PMBM), (4-methoxyphenoxy)methyl (p-AOM),guaiacolmethyl (GUM), t-butoxymethyl, 4-pentenyloxymethyl (POM),siloxymethyl, 2-methoxyethoxymethyl (MEM), 2,2,2-trichloroethoxymethyl,bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl (SEMOR),tetrahydropyranyl (THP), 3-bromotetrahydropyranyl,tetrahydrothiopyranyl, 1-methoxycyclohexyl, 4-methoxytetrahydropyranyl(MTHP), 4-methoxytetrahydrothiopyranyl, 4-methoxytetrahydrothiopyranylS,S-dioxide,1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl(CTMP),1,4-dioxan-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl,2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl,1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl,1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl,2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-(phenylselenyl)ethyl,t-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl,benzyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl,p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl,p-phenylbenzyl, 2-picolyl, 4-picolyl, 3-methyl-2-picolyl N-oxido,diphenylmethyl, p,p′-dinitrobenzhydryl, 5-dibenzosuberyl,triphenylmethyl, α-naphthyldiphenylmethyl,p-methoxyphenyldiphenylmethyl, di(p-methoxyphenyl)phenylmethyl,tri(p-methoxyphenyl)methyl, 4-(4′-bromophenacyloxyphenyl)diphenylmethyl,4,4′,4″-tris(4,5-dichlorophthalimidophenyl)methyl,4,4′,4″-tris(levulinoyloxyphenyl)methyl,4,4′,4″-tris(benzoyloxyphenyl)methyl,3-(imidazol-1-yl)bis(4′,4″-dimethoxyphenyl)methyl,1,1-bis(4-methoxyphenyl)-1′-pyrenylmethyl, 9-anthryl,9-(9-phenyl)xanthenyl, 9-(9-phenyl-10-oxo)anthryl,1,3-benzodithiolan-2-yl, benzisothiazolyl S,S-dioxido, trimethylsilyl(TMS), triethylsilyl (TES), triisopropylsilyl (TIPS),dimethylisopropylsilyl (IPDMS), diethylisopropylsilyl (DEIPS),dimethylthexylsilyl, t-butyldimethylsilyl (TBDMS), t-butyldiphenylsilyl(TBDPS), tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl,diphenylmethylsilyl (DPMS), t-butylmethoxyphenylsilyl (TBMPS), formate,benzoylformate, acetate, chloroacetate, dichloroacetate,trichloroacetate, trifluoroacetate, methoxyacetate,triphenylmethoxyacetate, phenoxyacetate, p-chlorophenoxyacetate,3-phenylpropionate, 4-oxopentanoate (levulinate),4,4-(ethylenedithio)pentanoate (levulinoyldithioacetal), pivaloate,adamantoate, crotonate, 4-methoxycrotonate, benzoate, p-phenylbenzoate,2,4,6-trimethylbenzoate (mesitoate), alkyl methyl carbonate,9-fluorenylmethyl carbonate (Fmoc), alkyl ethyl carbonate, alkyl2,2,2-trichloroethyl carbonate (Troc), 2-(trimethylsilyl)ethyl carbonate(TMSEC), 2-(phenylsulfonyl)ethyl carbonate (Psec),2-(triphenylphosphonio) ethyl carbonate (Peoc), alkyl isobutylcarbonate, alkyl vinyl carbonate alkyl allyl carbonate, alkylp-nitrophenyl carbonate, alkyl benzyl carbonate, alkyl p-methoxybenzylcarbonate, alkyl 3,4-dimethoxybenzyl carbonate, alkyl o-nitrobenzylcarbonate, alkyl p-nitrobenzyl carbonate, alkyl S-benzyl thiocarbonate,4-ethoxy-1-napththyl carbonate, methyl dithiocarbonate, 2-iodobenzoate,4-azidobutyrate, 4-nitro-4-methylpentanoate, o-(dibromomethyl)benzoate,2-formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl,4-(methylthiomethoxy)butyrate, 2-(methylthiomethoxymethyl)benzoate,2,6-dichloro-4-methylphenoxyacetate,2,6-dichloro-4-(1,1,3,3-tetramethylbutyl)phenoxyacetate,2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate,isobutyrate, monosuccinoate, (E)-2-methyl-2-butenoate,o-(methoxycarbonyl)benzoate, α-naphthoate, nitrate, alkylN,N,N′,N′-tetramethylphosphorodiamidate, alkyl N-phenylcarbamate,borate, dimethylphosphinothioyl, alkyl 2,4-dinitrophenylsulfenate,sulfate, methanesulfonate (mesylate), benzylsulfonate, and tosylate(Ts). Exemplary protecting groups are detailed herein, however, it willbe appreciated that the present disclosure is not intended to be limitedto these protecting groups; rather, a variety of additional equivalentprotecting groups can be readily identified using the above criteria andutilized in the method of the present disclosure. Additionally, avariety of protecting groups are described in Protecting Groups inOrganic Synthesis, T. W. Greene and P. G. M. Wuts, 3^(rd) edition, JohnWiley & Sons, 1999, the entirety of which is incorporated herein byreference.

As described herein, compounds of the invention may contain “optionallysubstituted” moieties. In general, the term “substituted”, whetherpreceded by the term “optionally” or not, means that one or morehydrogens of the designated moiety are replaced with a suitablesubstituent. Unless otherwise indicated, an “optionally substituted”group may have a suitable substituent at each substitutable position ofthe group, and when more than one position in any given structure may besubstituted with more than one substituent selected from a specifiedgroup, the substituent may be either the same or different at everyposition. Combinations of substituents envisioned by this invention arepreferably those that result in the formation of stable or chemicallyfeasible compounds. The term “stable”, as used herein, refers tocompounds that are not substantially altered when subjected toconditions to allow for their production, detection, and, in certainembodiments, their recovery, purification, and use for one or more ofthe purposes disclosed herein.

Suitable monovalent substituents on a substitutable carbon atom of an“optionally substituted” group are independently halogen;—(CH₂)₀₋₄R^(∘); —(CH₂)₀₋₄OR^(∘); —O—(CH₂)₀₋₄C(O)OR^(∘);—(CH₂)₀₋₄CH(OR^(∘))₂; —(CH₂)₀₋₄SR^(∘); —(CH₂)₀₋₄Ph, which may besubstituted with R^(∘); —(CH₂)₀₋₄O(CH₂)₀₋₁Ph which may be substitutedwith R^(∘); —CH═CHPh, which may be substituted with R^(∘); —NO₂; —CN;—N₃; —(CH₂)₀₋₄N(R^(∘))₂; —(CH₂)₀₋₄N(R^(∘))C(O)R^(∘); —N(R^(∘))C(S)R^(∘);—(CH₂)₀₋₄N(R^(∘))C(O)NR^(∘) ₂; —N(R^(∘))C(S)NR^(∘) ₂;—(CH₂)₀₋₄N(R^(∘))C(O)OR^(∘); —N(R^(∘))N(R^(∘))C(O)R^(∘);—N(R^(∘))N(R^(∘))C(O)NR^(∘) ₂; —N(R^(∘))N(R^(∘))C(O)OR^(∘);—(CH₂)₀₋₄C(O)R^(∘); —C(S)R^(∘); —(CH₂)₀₋₄C(O)OR^(∘);—(CH₂)₀₋₄C(O)N(R^(∘))₂; —(CH₂)₀₋₄C(O)SR^(∘); —(CH₂)₀₋₄C(O)OSiR^(∘) ₃;—(CH₂)₀₋₄OC(O)R^(∘); —OC(O)(CH₂)₀₋₄SR—, SC(S)SR^(∘);—(CH₂)₀₋₄SC(O)R^(∘); —(CH₂)₀₋₄C(O)NR^(∘) ₂; —C(S)NR^(∘) ₂; —C(S)SR^(∘);—SC(S)SR^(∘), —(CH₂)₀₋₄OC(O)NR^(∘) ₂; —C(O)N(OR^(∘)) R^(∘);—C(O)C(O)R^(∘); —C(O)CH₂C(O)R^(∘); —C(NOR^(∘))R^(∘); —(CH₂)₀₋₄SSR^(∘);—(CH₂)₀₋₄S(O)₂R^(∘); —(CH₂)₀₋₄S(O)₂OR^(∘); —(CH₂)₀₋₄OS(O)₂R^(∘);—S(O)₂NR^(∘) ₂; —(CH₂)₀₋₄S(O)R^(∘); —N(R^(∘))S(O)₂NR^(∘) ₂;—N(R^(∘))S(O)₂R^(∘); —N(OR^(∘))R^(∘); —C(NH)NR^(∘) ₂; —P(O)₂R^(∘);—P(O)R^(∘) ₂; —OP(O)R^(∘) ₂; —OP(O)(OR^(∘))₂; SiR^(∘) ₃; —(C₁₋₄ straightor branched alkylene)O—N(R^(∘))₂; or —(C₁₋₄ straight orbranched)alkylene)C(O)O—N(R^(∘))₂, wherein each R^(∘)may be substitutedas defined below and is independently hydrogen, C₁₋₈ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur, or, notwithstanding the definition above, twoindependent occurrences of R^(∘), taken together with their interveningatom(s), form a 3- to 12-membered saturated, partially unsaturated, oraryl mono- or polycyclic ring having 0-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur, which may be substituted asdefined below.

Suitable monovalent substituents on R^(∘)(or the ring formed by takingtwo independent occurrences of R^(∘)together with their interveningatoms), are independently halogen, —(CH₂)₀₋₂R^(●), —(haloR^(●)),—(CH₂)₀₋₂OH, —(CH₂)₀₋₂OR^(●), —(CH₂)₀₋₂CH(OR^(●))₂; —O(haloR^(●)), —CN,—N₃, —(CH₂)₀₋₂C(O)R^(●), —(CH₂)₀₋₂C(O)OH, —(CH₂)₀₋₂C(O)OR^(●),—(CH₂)₀₋₄C(O)N(R^(∘))₂; —(CH₂)₀₋₂SR^(●), —(CH₂)₀₋₂SH, —(CH₂)₀₋₂NH₂,—(CH₂)₀₋₂NHR^(●), —(CH₂)₀₋₂NR^(●) ₂, —NO₂, —SiR^(●) ₃, —OSiR^(●) ₃,—C(O)SR^(●), —(C₁₋₄ straight or branched alkylene)C(O)OR^(●), or—SSR^(●)wherein each R^(●)is unsubstituted or where preceded by “halo”is substituted only with one or more halogens, and is independentlyselected from C₁₋₄ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5- to6-membered saturated, partially unsaturated, or aryl ring having 0-4heteroatoms independently selected from nitrogen, oxygen, or sulfur.Suitable divalent substituents on a saturated carbon atom ofR^(∘)include ═O and ═S.

Suitable divalent substituents on a saturated carbon atom of an“optionally substituted” group include the following: ═O, ═S, ═NNR*₂,═NNHC(O)R*, ═NNHC(O)OR*, ═NNHS(O)₂R*, ═NR*, ═NOR*, —O(C(R*₂))₂₋₃O—, or—S(C(R*₂))₂₋₃S—, wherein each independent occurrence of R* is selectedfrom hydrogen, C₁₋₆ aliphatic which may be substituted as defined below,or an unsubstituted 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur. Suitable divalent substituents that are bound tovicinal substitutable carbons of an “optionally substituted” groupinclude: —O(CR*₂)₂₋₃O—, wherein each independent occurrence of R* isselected from hydrogen, C₁₋₆ aliphatic which may be substituted asdefined below, or an unsubstituted 5- to 6-membered saturated, partiallyunsaturated, or aryl ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R* include halogen,—R^(●), -(haloR^(●)), —OH, —OR^(●), —O(haloR^(●)), —CN, —C(O)OH,—C(O)OR^(●), —NH₂, —NHR^(●), —NR^(●) ₂, or —NO₂,

wherein each R^(●)is unsubstituted or where preceded by “halo” issubstituted only with one or more halogens, and is independently C₁₋₄aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5- to 6-membered saturated,partially unsaturated, or aryl ring having 0-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur.

Suitable substituents on a substitutable nitrogen of an “optionallysubstituted” group include —R^(†), —NR^(†) ₂, —C(O)R^(†), —C(O)OR^(†),—C(O)C(O)R^(†), —C(O)CH₂C(O)R^(†), —S(O)₂R^(†), —S(O)₂NR^(†) ₂,—C(S)NR^(†) ₂, —C(NH)NR^(†) ₂, or —N(R^(†))S(O)₂R^(†); wherein eachR^(†) is independently hydrogen, C₁₋₆ aliphatic which may be substitutedas defined below, unsubstituted —OPh, or an unsubstituted 5- to6-membered saturated, partially unsaturated, or aryl ring having 0-4heteroatoms independently selected from nitrogen, oxygen, or sulfur, or,notwithstanding the definition above, two independent occurrences ofR^(†), taken together with their intervening atom(s) form anunsubstituted 3- to 12-membered saturated, partially unsaturated, oraryl mono- or bicyclic ring having 0-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur. A substitutable nitrogen maybe substituted with three R^(†) substituents to provide a chargedammonium moiety —N⁺(R^(†))₃, wherein the ammonium moiety is furthercomplexed with a suitable counterion.

Suitable substituents on the aliphatic group of R^(†) are independentlyhalogen, —R^(●), -(haloR^(●)), —OH, —OR^(●), —O(haloR^(●)), —CN,—C(O)OH, —C(O)OR^(●), —NH₂, —NHR^(●), —NR^(●) ₂, or —NO₂, wherein eachR^(●)is unsubstituted or where preceded by “halo” is substituted onlywith one or more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5- to 6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

As used herein, the term “catalyst” refers to a substance the presenceof which increases the rate and/or extent of a chemical reaction, whilenot being consumed or undergoing a permanent chemical change itself.

In some chemical structures herein, substituents are shown attached to abond which crosses another bond of a depicted molecule. This means thatone or more of the substituents may be attached to the molecule at anyavailable position (usually in place of a hydrogen atom of the parentstructure). In cases where an atom of a molecule so substituted has twosubstitutable positions, two groups may be present on the same ringatom. When more than one substituent is present, each is definedindependently of the others, and each may have a different structure. Incases where the substituent shown crossing a bond of the molecule is —R,this has the same meaning as if the ring were said to be “optionallysubstituted” as described in the preceding paragraph.

Any tetradentate ligand capable of complexing a metal atom which isformed from a diamine condensed with two molar equivalents of aβ-hydroxy carbonyl compound herein is included in the class of salensand defined as a “salen” or “salen ligand.” A salen ligand may besymmetrical meaning that the diamine is condensed with two identicalβ-hydroxy carbonyl compounds or a salen ligand may be nonsymmetricalmeaning that the diamine is condensed with two different β-hydroxycarbonyl compounds. In some embodiments, the terms “salen” and “salenligand” refer to the structural elements ofN,N′-ethylenebis(salicylimine) (CAS 94-93-9), or an analog thereof, thatare necessary to form a tetradentate ligand capable of complexingmetals. The term “salen complex” refers to the complex formed between a“salen” or “salen ligand” and a metal.

In salen complexes having dianionic counterions, the counterion may bebound in a bidentate manner to a metal. As a result, the tetradentatesalen ligand which is often planar and occupies the equatorial sites ofan octagonal metal complex, will have one of its heteroatoms out ofplane and occupying an apical coordination site on a metal. Therefore,certain compounds of the present invention can exist in various isomericforms, wherein the metal atom is a stereocenter, for example:

where each

represents a salen ligand:

and where M, R^(G) and R^(J) are as defined herein

Thus, inventive compounds and compositions thereof may be in the form ofan individual enantiomer, diastereomer or geometric isomer, or may be inthe form of a mixture of these isomers.

The term “TBD” refers to 1,4,9-triazabicyclo[4.4.0]dec-9-ene.

The term “MeTBD” refers to 1-methyl-1,4,9-triazabicyclo[4.4.0]dec-9-ene.

The term “TBO” refers to 1,4,6-triazabicyclo[3.3.0]oct-4-ene.

The term “molecular weight population” refers to a distinct elution peakobservable in a gel permeation chromatogram; monomodal polymer sampleshave substantially one such peak, while bimodal polymer samples have twodistinctly observable peaks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an NMR spectrum of compound N, a cobalt(III)salen complexwith an oxalate counterion.

FIG. 2 depicts an NMR spectrum of compound O, a cobalt(III)salen complexwith a malonate counterion.

FIG. 3 depicts an NMR spectrum of compound Q, a cobalt(III)salen complexwith a carbonate counterion.

FIG. 4 depicts an NMR spectrum of compound R, a cobalt(III)salen complexwith a carbonate counterion.

FIG. 5 depicts UV spectra. Top panel: UV-Vis spectrum of compound N, acobalt(III)salen complex with an oxalate counterion. Bottom panel:UV-Vis spectrum of compound O, a cobalt(III)salen complex with amalonate counterion.

FIG. 6 depicts UV spectra. Top panel: UV-Vis spectrum of compound Q, acobalt(III)salen complex with a carbonate counterion. Bottom panel:UV-Vis spectrum of compound R, a cobalt(III)salen complex with acarbonate counterion.

FIG. 7 depicts an x-Ray structure of compound Q, a Co(III) salen complexwith a carbonate counterion.

FIG. 8a-c shows GPC traces of prior art aliphatic polycarbonates (APCs).FIGS. 8a and 8b are reproduced from JACS. 2007, 129, 8082-8083,supporting info. FIG. 8c is reproduced from Macromolecules, 2010, 43(3), pp 1396-1402 supporting info.

FIG. 9a-c shows GPC traces of monomodal APCs of the present inventionalong with a comparative polymer made according to the prior art.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides, among other things, the recognition thata dianionic counterion can facilitate economical isolation andpurification of Cr(III) and Co(III) salen complexes by causingprecipitation of the complex directly from a reaction mixture. Thepresent invention further provides, among other things, a method for theprecipitation of tetradentate salen metal complexes by the use of adianionic counterion for the complex.

In certain embodiments, the present invention provides salen Cr(III) orCo(III) complexes characterized in that they comprise a dianioniccouterion. In certain embodiments, such complexes are furthercharacterized in that they comprise one or more nitrogen-, phosphorous-,or arsenic-containing functional groups covalently tethered to the salenligand (for example such as those disclosed in published PCTapplications WO/2010/022388 and WO 2008/136591 each of which isincorporated herein by reference). In certain embodiments, suchnitrogen-, phosphorous-, or arsenic-containing functional groupscomprise cationic groups (or moieties that can be protonated to formcationic groups). In certain embodiments, such tethered cationic orprotonated groups balance a negative charge from the dianion-coordinatedto the complex. In certain embodiments, the negative charge thusbalanced resides on the metal atom. In other embodiments, the negativecharge thus balanced may reside on an atom other than the metal atom,including an atom of the dianion.

In certain embodiments, where a tethered group comprises anitrogen-containing functional group, the group comprises a quaternarynitrogen atom. In other embodiments, covalently tethered cationic groupscomprise a protonated nitrogen atom. In certain embodiments, covalentlytethered cationic groups comprise ammonium salts. In certainembodiments, covalently tethered cationic groups comprise guanidiniumsalts. In certain embodiments, covalently tethered cationic groupscomprise amidinium salts. In certain embodiments, covalently tetheredcationic groups comprise arsonium salts.

In certain embodiments, the metal complexes encompassed by the presentinvention comprise complexes described in WO 2010/022388 and/or WO2008/136591 wherein one or more mono-anionic counterions of thecatalysts disclosed therein are replaced by a dianion as describedherein. The entire content of each of these documents is incorporatedherein by reference.

Metal Complexes

In certain embodiments, provided compounds are of Formula I:

-   -   wherein:    -   M is Co or Cr;    -   R^(1a), R^(1a′), R^(2a), R^(2a′), R^(3a), and R^(3a′) are        independently a        (Z)_(m) group, hydrogen, R, halogen, —OR, —NR₂, —SR, —CN, —NO₂,        —SO₂R, —SOR, —SO₂NR₂; —CNO, —NRSO₂R, —NCO, —Ni, —SiR₃, —C(O)R,        —NRC(O)R, —OC(O)R, —CO₂R, —OC(O)N(R)₂, —C(O)NR₂, —NRC(O)NR—,        —NRC(O)OR; or an optionally substituted radical selected from        the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic;        phenyl; a 3- to 8-membered saturated or partially unsaturated        monocyclic carbocycle, a 7- to 14-membered saturated, partially        unsaturated or aromatic polycyclic carbocycle; a 5- to        6-membered monocyclic heteroaryl ring having 1-4 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; a 3- to        8-membered monocyclic saturated or partially unsaturated        heterocyclic ring having 1-3 heteroatoms independently selected        from nitrogen, oxygen, or sulfur; a 6- to 12-membered polycyclic        saturated or partially unsaturated heterocycle having 1-5        heteroatoms independently selected from nitrogen, oxygen, or        sulfur; or an 8- to 10-membered bicyclic heteroaryl ring having        1-5 heteroatoms independently selected from nitrogen, oxygen, or        sulfur; where each R is independently hydrogen, an optionally        substituted radical selected the group consisting of acyl;        carbamoyl; arylalkyl; phenyl; C₁₋₁₂ aliphatic; C₁₋₁₂        heteroaliphatic; a 3- to 8-membered saturated or partially        unsaturated monocyclic carbocycle, a 7- to 14-membered        saturated, partially unsaturated or aromatic polycyclic        carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having        1-4 heteroatoms independently selected from nitrogen, oxygen, or        sulfur; a 3- to 8-membered monocyclic saturated or partially        unsaturated heterocyclic ring having 1-3 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; an 8-        to 10-membered bicyclic heteroaryl ring having 1-5 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; an        oxygen protecting group; and a nitrogen protecting group; or:        two R on the same nitrogen atom are taken with the nitrogen to        form a 3- to 7-membered heterocyclic ring, and wherein any of        [R^(2a′) and R^(3a′)], [R^(2a) and R^(3a)], [R^(1a) and R^(2a)],        and [R^(1a′) and R^(2a′)] may optionally be taken together with        the carbon atoms to which they are attached to form one or more        rings which may in turn be optionally substituted as defined        above, or substituted with one or more R groups; and    -   R^(G) is selected from the group consisting of:

-   -   R^(J) is a bivalent linker selected from the group consisting        of: —C(O)—, —C(O)C(O)—, —C(O)—R^(H)—C(O)—, —SO—, —SO₂—,        —P(O)(OR^(J1))—, —P(O)R^(J1)—, —R^(J1)C═N—,        —C(O)—R^(H)—P(O)(OR^(J1))—, —C(O)—R^(H)—S(O)—,        —C(O)—R^(H)—S(O)₂—, —SO₂—R^(H)—P(O)(OR^(J1))—,        —SO—R^(H)—P(O)(OR^(J1))—, —C(O)R^(H)—;    -   where,        -   R^(c) groups are optionally present, and if present are,            independently at each occurrence selected from the group            consisting of: a            (Z)_(m) group, halogen, —OR, —NR₂, —SR, —CN, —NO₂, —SO₂R,            —SOR, —SO₂NR₂; —CNO, —NRSO₂R, —NCO, —N₃, —SiR₃, —C(O)R,            —NRC(O)R, —OC(O)R, —CO₂R, —OC(O)N(R)₂, —C(O)NR₂, —NRC(O)NR—,            —NRC(O)OR; or an optionally substituted radical selected            from the group consisting of arylalkyl; phenyl; C₁₋₂₀            aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered            saturated or partially unsaturated monocyclic carbocycle, a            7- to 14-membered saturated, partially unsaturated or            aromatic polycyclic carbocycle; a 5- to 6-membered            monocyclic heteroaryl ring having 1-4 heteroatoms            independently selected from nitrogen, oxygen, or sulfur; a            3- to 8-membered monocyclic saturated or partially            unsaturated heterocyclic ring having 1-3 heteroatoms            independently selected from nitrogen, oxygen, or sulfur; an            8- to 10-membered bicyclic heteroaryl ring having 1-5            heteroatoms independently selected from nitrogen, oxygen, or            sulfur; where two or more R^(c) groups may be taken together            with the carbon atoms to which they are attached and any            intervening atoms to form one or more optionally substituted            rings; and where when two R^(c) groups are attached to the            same carbon atom, they may be taken together along with the            carbon atom to which they are attached to form a moiety            selected from the group consisting of: a 3- to 8-membered            spirocyclic ring, a carbonyl, an oxime, a hydrazone, an            imine; and an optionally substituted alkene;        -   R^(d) groups are optionally present, and if present are,            independently at each occurrence selected from the group            consisting of: a            (Z)_(m) group, halogen, —R, —OR, —NR₂, —SR, —CN, —NO₂,            —SO₂R, —SOR, —SO₂NR₂; —CNO, —NRSO₂R, —NCO, —N₃, —SiR₃,            —C(O)R, —NRC(O)R, —OC(O)R, —CO₂R, —OC(O)N(R)₂, —C(O)NR₂,            —NRC(O)NR—, —NRC(O)OR; or an optionally substituted group            selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀            heteroaliphatic having 1-4 heteroatoms independently            selected from the group consisting of nitrogen, oxygen, and            sulfur; 6-10-membered aryl; 5-10-membered heteroaryl having            1-4 heteroatoms independently selected from nitrogen,            oxygen, or sulfur; and 4-7-membered heterocyclic having 1-2            heteroatoms independently selected from the group consisting            of nitrogen, oxygen, and sulfur; where two or more R^(c)            groups may be taken together with the carbon atoms to which            they are attached and any intervening atoms to form one or            more optionally substituted rings optionally containing one            or more heteroatoms;        -   R^(c′) is, independently at each occurrence, —H, or R^(c);        -   Y is a bivalent linker selected from the group consisting            of: —(CR^(c′) ₂)_(q′)—; —NR—, —N(R)C(O)—, —C(O)NR—, —O—,            —C(O)—, —OC(O)—, —C(R)₂—, —C(O)O—, —S—, —SO—, —SO₂—,            —C(═S)—, —C(═NR)—, or —N═N—; a polyether; C₁₋₆ aliphatic; a            C₃ to C₈ substituted or unsubstituted carbocycle; and a 3-            to 8-membered substituted or unsubstituted heterocycle;        -   R^(H) is selected from the group consisting of R^(G) and            —(CR^(c′) ₂)_(q′),        -   R^(J1) is independently at each occurrence selected from the            group consisting of: hydrogen, a metal atom, an optionally            substituted radical selected from the group consisting of            acyl; carbamoyl; arylalkyl; phenyl; C₁₋₁₂ aliphatic; C₁₋₁₂            heteroaliphatic; 4- to 7-membered heterocyclyl; a 5- to            6-membered monocyclic heteroaryl ring having 1-4 heteroatoms            independently selected from nitrogen, oxygen, or sulfur; or            an oxygen protecting group; and        -   q′ is an integer from 1 to 6;        -   q is from 0 to 5, inclusive;        -   x is 0, 1, or 2; and        -   δ represents the net charge of the metal complex exclusive            of any non-covalently bound counterions and may be any            number between −1 and +5;            (Z)_(m) represents one or more activating moieties attached            to the multidentate ligand, where            is a linker moiety covalently coupled to the ligand, each Z            is an activating functional group; and m is an integer from            1 to 4 representing the number of Z groups present on an            individual linker moiety.

In some embodiments, at least one of [R^(2a) and R^(3a)] and [R^(2a′)and R^(3a′)] are taken together to form a ring. In some embodiments,both [R^(2a) and R^(3a)] and [R^(2a′) and R^(3a′)] are taken together toform rings. In some embodiments, the rings formed by [R^(2a) and R^(3a)]and/or [R^(2a′) and R^(3a′)] are substituted phenyl rings.

In certain embodiments, M is chromium. In certain embodiments, M isCr(III), in certain embodiments, M is cobalt. In certain embodiments, Mis Co(III).

In certain embodiments, one or more of R^(1a), R^(1a′), R^(2a), R^(2a′),R^(3a), and R^(3a′) are independently a

(Z)_(m) group.

In some embodiments, Y is a bivalent linker selected from C₁₋₆ aliphaticor a C₃ to C₈ substituted or unsubstituted carbocycle. In some,embodiments, Y is C₁₋₆ alkyl or C₁₋₆ alkenyl.

In certain embodiments of provided metal complexes with a dianioniccounterion, a salen complex has a structure selected from the groupconsisting of:

-   -   wherein each of M, R^(G), R^(c), R^(d), R^(J), R^(1a), R^(1a′),        and δ is as defined above and described in classes and        subclasses herein; and        -   R^(4a), R^(4a′), R^(5a), R^(5a′), R^(6a), R^(6a′), R^(7a),            and R^(7a′) are each independently hydrogen, or an R^(d)            group wherein [R^(1a) and R^(4a)], [R^(1a′) and R^(4a′)] and            any two adjacent R^(4a), R^(4a′), R^(5a), R^(5a′), R^(6a),            R^(6a′), R^(7a), and R^(7a′) groups can be taken together            with intervening atoms to form one or more optionally            substituted rings;

In some embodiments of complexes of formulae Ia through Id, R^(1a),R^(1a′), R^(4a), R^(4a′), R^(6a), and R^(6a′) are each —H. In someembodiments, R^(5a), R^(5a′), R^(7a) and R^(7a′) are each optionallysubstituted C₁-C₁₂ aliphatic. In some embodiments, R^(4a), R^(4a′),R^(5a), R^(5a′), R^(6a), R^(6a′), R^(7a), and R^(7a′) are eachindependently selected from the group consisting of: —H, —SiR₃; methyl,ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, t-butyl, isoamyl, t-amyl,thexyl, and trityl. In some embodiments, R^(1a), R^(1a′), R^(4a),R^(4a′), R^(6a), and R^(6a′) are each —H. In some embodiments, R^(7a) isselected from the group consisting of —H; methyl; ethyl; n-propyl;i-propyl; n-butyl; sec-butyl; t-butyl; isoamyl; t-amyl; thexyl; andtrityl. In some embodiments, R^(5a) and R^(7a) are independentlyselected from the group consisting of —H; methyl; ethyl; n-propyl;i-propyl; n-butyl; sec-butyl; t-butyl; isoamyl; t-amyl; thexyl; andtrityl. In certain embodiments, one or more of R^(5a), R^(5a′), R^(7a)and R^(7a′) is a

(Z)_(m) group. In some embodiments, R^(5a) and R^(5a′) are a

(Z)_(m) group. In some embodiments, one of R^(5a) or R^(5a′) is a

(Z)_(m) group. In some embodiments, one of R^(7a) or R^(7a′) is a

(Z)_(m) group.

In certain embodiments of complexes having formulae Ia through Id, atleast one of the phenyl rings comprising a salicylaldehyde-derivedportion of the salen ligand is independently selected from the groupconsisting of:

wherein

(Z)_(m) is as defined above and described in the embodiments andexamples herein.

In certain embodiments, there is an activating moiety tethered to theposition ortho to a metal-bound oxygen substituent of one or both of thesalicylaldehyde-derived phenyl rings of a salen ligand as in formulaeIa-1 and Ia-2:

-   -   wherein M, R^(d), R^(4a), R^(4a′), R^(5a), R^(5a′), R^(6a),        R^(6a′), R^(G), R^(J), δ, and        (Z)_(m) are as defined above and described in the embodiments        and examples herein.

In certain embodiments of compounds having formulae Ia-1 or Ia-2,R^(4a), R^(4a′), R^(6a), and R^(6a′) are each hydrogen, and R^(5a),R^(5a′) are, independently, optionally substituted C₁-C₂₀ aliphatic.

In certain embodiments of complexes Ia-1 and Ia-2, at least one of thephenyl rings comprising a salicylaldehyde-derived portion of a catalystis independently selected from the group consisting of:

wherein

(Z)_(m) is as described herein.

In certain embodiments, there is an activating moiety tethered to theposition para to the phenolic oxygen of one or both of asalicylaldehyde-derived phenyl rings of the salen ligand as instructures Ia-3 and Ia-4:

-   -   wherein R^(d), R^(4a), R^(4a′), R^(6a), R^(6a′) R^(7a), R^(7a′),        R^(G), R^(J), δ, and        (Z)_(m) are as defined above and described in the embodiments        and examples herein.

In certain embodiments of compounds having formulae Ia-3 or Ia-4,R^(4a), R^(4a′), R^(6a), and R^(6a′) are hydrogen, and each R^(7a),R^(7a′) is, independently, optionally substituted C₁-C₂₀ aliphatic.

In certain embodiments of catalysts Ia-3 or Ia-4, at least one of thephenyl rings comprising a salicylaldehyde-derived portion of a catalystis independently selected from the group consisting of:

-   -   wherein        (Z)_(m) is as described herein.

In some embodiments, there are activating moieties tethered to thepositions ortho and para to the phenolic oxygen of one or both of thesalicylaldehyde-derived phenyl rings of a salen ligand as in formulaeIa-5 and Ia-6:

-   -   wherein M, R^(d), R^(4a), R^(4a′), R^(6a), R^(6a′) R^(G), R^(J),        δ, and        (Z)_(m) are as defined above and described in the embodiments        and examples herein.

In certain embodiments of compounds having formulae Ia-5 and Ia-6, eachR^(6a), R^(6a′), R^(4a) and R^(4a′) is, independently, hydrogen oroptionally substituted C₁-C₂₀ aliphatic.

In certain embodiments of compounds having formulae Ia-5 and Ia-6, eachR^(6a), R^(6a′), R^(4a), and R^(4a′) is hydrogen.

In certain embodiments, in the salen ligands of catalysts Ia-1 throughIa-6 above, the moiety:

is selected from the group:

In certain embodiments, in the salen ligands of catalysts Ia-1 throughI-a6 above, the moiety:

is selected from the group:

Dianions

As noted above, the chromium and cobalt complexes of the presentinvention are characterized in that they comprise a dianionic counterionassociated with the metal atom, and/or optionally one or more cationicgroups that may be covalently tethered to the salen ligand.

In certain embodiments, the dianion comprises one or more groupsselected from the group consisting of: carbonate, carboxylate,dicarboxylate, sulfur-containing anions, phosphorous-containing anions,and combinations of two or more of these.

In certain embodiments, a dianion

bound to the metal in a provided compound forms the moiety:

where R^(J) is as defined above and described in the examples andembodiments herein.

In certain embodiments, in any of the chromium complexes described aboveincluding compounds of Formulae Ia through Id and Ia-1 through Ia-6, themoiety

is carbonate. In certain embodiments, the moiety

is oxalate. In certain embodiments, the moiety

is malonate. In certain embodiments, the moiety

is maleate. In certain embodiments, the moiety

is fumarate.

In certain embodiments, the moiety

is succinate. In certain embodiments, in compounds of Formulae Iathrough Id and Ia-1 through Ia-6, the moiety

is glutarate. In certain embodiments, the moiety

is phthalate.

In some embodiments, R^(J) in any of the compounds described herein is—C(O)—. In some embodiments, R^(J) is —C(O)C(O)—. In some embodiments,R^(J) is —C(O)—R^(H)—C(O)—. In some embodiments, R^(J) is —SO—. In someembodiments, R^(J) is —SO₂—. In some embodiments, R^(J) is—P(O)(OR^(J1))—. In some embodiments, R^(J) is —P(O)R^(J1)—. In someembodiments, R^(J) is —R^(J1)C═N—. In some embodiments, R^(J) is—C(O)—R^(H)—P(O)(OR^(J1))—. In some embodiments, R^(J) is—C(O)—R^(H)—S(O)—. In some embodiments, R^(J) is —C(O)—R^(H)—S(O)₂—. Insome embodiments, R^(J) is —SO₂—R^(H)—P(O)(OR^(J1))—. In someembodiments, R^(J) is —SO—R^(H)—P(O)(OR^(J1))—. In some embodiments,R^(J) is —C(O)R^(H)—.

In some embodiments, R^(H) is

wherein q′ is from 1 to 6, wherein R^(d) is as defined above. In someembodiments, R^(H) is

wherein q′ is from 1 to 5. In some embodiments, R^(H) is

wherein q′ is from 1 to 4. In some embodiments, R^(H) is

wherein q′ is from 1 to 3. In some embodiments, R^(H) is

wherein q′ is from 1 to 2.

In some embodiments, R^(H) is

where R^(d), is as defined above. In some embodiments, R^(H) is

where R^(d), is as defined above. In some embodiments, R^(H) is

where R^(d), is as defined above.

In certain embodiments, where a R^(J) group comprises R^(c), R^(c′), orR^(d), the R^(c), R^(c′), and R^(d) group(s) are other than

(Z)_(m).

Tethered Moieties

As noted above, in certain embodiments, metal complexes of the presentinvention comprise one or more nitrogen- or phosphorous-containingfunctional groups covalently tethered to the salen ligand. In certainembodiments, these tethered functional groups are defined as

(Z)_(m) groups, where

represents the covalent tether (also referred to herein as a ‘linker,’ a‘linker moiety,’ or a ‘Z-linker’), each Z comprises a nitrogen-,phosphorous-, or arsenic-containing functional group, and m is aninteger of one or greater indicating how many such nitrogen-,phosphorous-, or arsenic-containing functional groups are attached to agiven linker.

In certain embodiments,

(Z)_(m) is defined by the embodiments found in Appendix A, infra. It isto be understood that definitions in the appendix are to be readindependently. For example, the definitions of R groups in the appendixmay differ from correspondingly designated R groups in the body of thespecification: in such instances, the definitions are to be regarded tobe independent and specific to the appendix. As such, a limitation on anR-group in an appendix is not necessarily intended to limit anydefinition provided in the specification and vice-versa.

In certain embodiments,

(Z)_(m) groups that may be present on complexes of the present inventioninclude those disclosed in WO/2010/022388 incorporated herein byreference.

In certain embodiments, each tether (or “Z-linker”) moiety

contains 1-30 atoms including at least one carbon atom, and optionallyone or more atoms selected from the group consisting of N, O, S, Si, B,and P. Additional embodiments of such linker moieties are described inAppendix A hereafter, and in descriptions of the embodiments, andexamples herein.

In certain embodiments, each Z is independently a quaternary amine, aguanadine, a guanidinium, an amidine, an amidinium, a neutral orcationic nitrogen-containing heterocycle or a variant or combination ofany of these. In certain embodiments, one or more Z groups comprises aguanidine, or more specifically a cyclic guanidine, or more specificallya bicyclic guanidine. In certain embodiments, one or more Z groupscomprises a guanidinium salt, or more specifically a cyclic guanidiniumsalt, or more specifically a bicyclic guanidinium salt. In certainembodiments, one or more Z groups comprises an amidine, or morespecifically a cyclic amidine, or more specifically a bicyclic amidine.In certain embodiments, one or more Z groups comprises a amidinium salt,or more specifically a cyclic amidinium salt, or more specifically abicyclic amidinium salt. In certain embodiments, one or more Z groupscomprises a quaternary ammonium group, or more specifically a trialkylammonium group, or more specifically a trimethylammonium group,triethylammonium group, tripropyl ammonium group, tributyl ammoniumgroup, a diethyl isopropyl ammonium group, a dimethylbutyl ammoniumgroup, or similar mixed lower-alkyl ammonium groups.

In certain embodiments, one or Z groups comprises a moiety having aformula selected from:

where R^(c) and R are as defined hereinabove and in the examples andembodiments described herein, and each of n and m is independently aninteger from 1 to 4 inclusive. In certain embodiments, one or more Zgroups are independently selected from the group consisting of:

In certain embodiments, one or more Z groups are independently selectedfrom the group consisting of:

where —R is as defined above.

In certain embodiments, one or more Z groups are independently selectedfrom the group consisting of:

In certain embodiments, one or more Z groups are independently selectedfrom the group consisting of:

In certain embodiments,

(Z)_(m) groups present on the metal complexes of the present inventionare selected from the group consisting of:

wherein each of R and n is as defined above and in the classes andsubclasses herein.

In certain embodiments, metal complexes of the present invention areselected from amongst those shown in Table 1. Many similar variationsand related compounds will be apparent to the skilled artisan.

TABLE 1

where X⁻ is independently at each occurrence any anion or a portion ofany dianionCharge Balances

As noted above, the chromium(III) and cobalt(III) salen complexesencompassed by the present invention comprise at least one dianion. Inthe certain embodiments, both negative charges of the dianion associatewith metal atom, leaving it with a net −1 charge. This net charge willneed to be balanced by a cation and this may occur in several ways. Incertain embodiments described above, there are one or more cationicgroups covalently tethered to the salen ligand. In certain embodimentsencompassing these examples, the −1 charge on the metal can be balancedby the +1 charge of one of these tethered cations. In other embodiments,the −1 formal charge on the metal atom can be balanced by a cation notcovalently bound to the complex, such cations may include any of themultitude known in the art including cationic metals, a proton, oniumsalts, and the like. Suitable metals include, but are not limited tosodium, lithium, potassium, zinc, magnesium, and transition metals. Incertain embodiments, the positive charge necessary to balance the −1charge, may come from a second molecule of a salen complex bearing a +1charge on the metal. Such complexes may thus comprise one dianionicanion as described above, and two molecules of a cationic metal complex.

In some embodiments, particularly where there is another metal atompresent, or where there are two or more cationic species covalentlytethered to the salen ligand, the complex may comprise a number ofadditional cations or anions as required to provide an overall neutralmolecule. For example, where there are two or more cationic speciestethered to the ligand, one may serve to offset the −1 charge present onthe chromium or cobalt atom associated with the dianion, while the othertethered cations may be associated with other anions. Likewise, asdescribed above, in certain embodiments, there may be an additionalmetal atom present (to balance the formal −1 charge on the chromium orcobalt atom, for example). In cases where the additional metal has a2+(or higher) charge, additional anions may also be present to balancethe charge(s) and provide a neutral compound. These other anions maycomprise additional equivalents of the dianic species described herein,or they may be other anions unrelated to the dianion on the metalcenter. Examples of other anions that may be associated under suchcircumstances include halide, nitrate, tetrafluoroborate, carboxylate,phenolate, azide, and the like.

It is thus to be understood that while not explicitly shown in everystructure or example, it is implied that the complexes described hereinwill be, in their isolated form, neutral compounds and that any numberof additional ions (whether shown or not) may be present to balancecharges shown or described in the complexes herein. For example, if asalen ligand is of formula Ia-6 and each (Z)_(m) moiety comprises onequaternary ammonium salt, the net charge of the complex (denoted δ inthe formula) will be 3+, the accounting that leads to this includes thenet +1 charge on the metal atom, the 2-charge of the dianion—O—R^(J)—O—, and four +1 charges for the four ammonium salts. There mustbe anions present to balance these 3 cations, and as described above,these may be provided by additional dianionic groups, or by other anionssuch as halide, carboxylate and the like. If the +3 charge is balancedby the dianions, it may arise that an excess charge from more than onechromium salen complex is balanced by the same dianion—for example, twochromium(III) or cobalt(III) complexes each having four tethered cationsmight form a complex with 5 dianions —O—R^(J)—O—, to form a neutralcomplex.

Catalyst Purification Methods

In certain embodiments, a salen complex of Formula I having a dianioniccounterion has the unexpected advantage of being easily isolated fromsolution by precipitation (or crystallization). Therefore, in anotheraspect, the present invention provides useful methods for thepurification of cobalt salen or chromium salen complexes. In certainembodiments the methods comprise a step of converting a cobalt orchromium complex having one or more mono-anioic counterions to acorresponding complex having one or more dianionic counterions. Incertain embodiments, the methods comprise the additional step ofisolating the complex comprising one or more dianionic counterions as asolid. In certain embodiments, the isolating step includes a substep ofprecipitating the metal complex from a solution. In certain embodiments,the precipitating step includes a substep of adding additional solventsto the solution. In certain embodiments, the precipitating step includesa substep of stripping a portion of the solvent from the solution. Incertain embodiments, the precipitating step includes one or moresubsteps selected from the group consisting of: cooling, heating, orstirring the solution.

In certain embodiments, the solution from which the complex having oneor more dianionic counterions is precipitated comprises one or morealcohols. In certain embodiments, the method comprises the step ofprecipitating the complex from a suitable alcohol solvent by addition ofa suitable ether and/or ester. Suitable alcohol solvents are known tothe skilled artisan and include, without limitation, C₁₋₄ alcohols. Insome embodiments, a suitable alcohol is selected from MeOH, EtOH, iPrOH,nPrOH, nBuOH, sec-BuOH, t-BuOH and mixtures of any two or more of these.Suitable ethers are known to the skilled artisan and include, withoutlimitation, diethyl ether, MTBE, THF, methyl cyclopentyl ether,diisopropyl ether, di-n-butyl ether, 1,4-dioxane, higher weight ethers,and mixtures of any two or more of these. Suitable esters are also knownto the skilled artisan and include, without limitation, methyl acetate,ethyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate,ethyl propionate, higher weight esters, and mixtures of any two or moreof these.

In certain embodiments, a salen complex of Formula I with a dianioniccounterion is precipitated from a mixture of a suitable alcohol solventand a suitable alkyl ester solvent in any relative proportion byaddition of a suitable ether or more ester solvent. Suitable alcoholsolvents are known to the skilled artisan and include, withoutlimitation, C₁₋₄ alcohols. In some embodiments, a suitable alcohol isselected MeOH, EtOH, iPrOH, nPrOH, nBuOH, sec-BuOH, t-BuOH and mixturesof any two or more of these. Suitable alkyl esters are known to theskilled artisan and include, without limitation, MeOAc, EtOAc, iPrOAc,nPrOAc, nBuOAc, sec-BuOAc, and mixtures of any two or more of these.Suitable ethers are known to the skilled artisan and include, withoutlimitation, ether, MTBE, THF, methyl cyclopentyl ether, diisopropylether, di-n-butyl ether, 1,4-dioxane, higher weight ethers, and mixturesof any two or more of these.

In certain embodiments, a salen complex of Formula I with a dianioniccounterion is precipitated from a mixture of a suitable alcohol solventand toluene in any relative proportion by addition of a suitable ether.Suitable alcohol solvents are known to the skilled artisan and include,without limitation, C₁₋₄ alcohols. In some embodiments, a suitablealcohol is selected from MeOH, EtOH, iPrOH, nPrOH, nBuOH, and sec-BuOH.Suitable ethers are known to the skilled artisan and include, withoutlimitation, MTBE, THF, methyl cyclopentyl ether, diisopropyl ether,di-n-butyl ether, 1,4-dioxane, and higher weight ethers.

In certain embodiments of compounds of Formula I, the precipitated metalsalen catalyst with a dianionic counterion obtained by filtration ischaracterized in that it is green in color.

In certain embodiments of compounds of Formula I, the precipitated salencatalyst with dianionic counterion obtained by filtration has anabsorption spectrum in the range of 195-700 nm with four maxima(λ_(max)). In some embodiments, ranges for the maxima are 195-205 nm(λ_(max1)), 225-245 nm (λ_(max2)), 255-270 nm (λ_(max3)), and 390-425 nm(λ_(max4)).

Polymer Compositions

One of the advantages of metal complex catalysts for epoxide CO₂copolymerization (i.e. as opposed to heterogenous zinc-based catalystsor double metal cyanide catalysts) is that they provide polymers with ahigh percentage of carbonate linkages (i.e. few ether linkages) andnarrow molecular weight distributions. However, it is well known in theart while that, even though the resulting polymers have narrow molecularweight distributions, the polymers invariably have a bimodal molecularweight distribution. It is also understood why this is so. The firststep in epoxide CO₂ copolymerization with this class of catalystsconsists of epoxide ring-opening by the anion associated with the metalatom of the catalytic complex. This anion is commonly referred to as apolymerization initiator. During polymerization the initiator opens anepoxide and is thereby covalently bound to the end of the polymer chainwhich then grows from the oxygen atom of the ring-opened epoxide,propagation continues in one direction to yield the final polymer chain.

It is also known that chain transfer agents can be added to epoxide CO₂copolymerizations and that their presence results in the formation ofmore than one polymer chain per catalyst molecule with a correspondingdecrease in the average molecular weight of the polymer chains formed.Chain transfer agents with more than one nucleophilic site result inpolymer chains that propagate in two or more directions and whichtherefore gain molecular weight at a higher rate than the chainsinitiated with a monoanion. Since these are living polymerizations andwater is can act as a chain transfer agent, the polymers contain apopulation of chains initiated by water which grow at approximatelytwice the rate of chains initiated by anions from the catalyticcomplexes. Without being bound by theory, or thereby limiting the scopeof this invention, it is believed the bimodal characteristics prior artaliphatic polycarbonate polymer compositions are explained by amechanism such as that shown in Scheme 1 which depicts thecopolymerization of propylene oxide and CO₂ by with a prior art catalysthaving a mono-anionic initiator (acetate):

Since it is impossible to completely exclude water from epoxide CO₂polymerization mixtures, the prior art aliphatic polycarbonates have hadbimodal molecular weight distributions. For representative examples seefor example (J. AM. CHEM. SOC. 2007, 129, 8082-8083, and supportinginfo.; and Macromolecules, 2010, 43 (3), pp 1396-1402 and supportinginfo) and the GPC traces of prior art polymers shown FIGS. 8a-8c . TheGPC traces in FIGS. 8a and 8b show PPC made with a catalyst havingmultiple dinitrophenolate initiators. The polymers show the bimodalitytypical of this class of polymer and two molecular weight populationsare clearly discernable in each chromatogram. The GPC trace in FIG. 8cshows PCHC (poly(cyclohexane carbonate) made with a similar catalyst.Again, the polymer is exhibits bimodality in its molecular weightdistribution.

During epoxide CO₂ copolymerizations, water is invariably present in thereaction mixtures and it has therefore been impossible to obtain trulyunimodal aliphatic polycarbonates using this class of catalyst. This isparticularly true for high molecular weight polymers where the catalystmust be provided in a very small molar ratio relative to the epoxide(e.g. 1:10,000 or less) and where even low parts-per-million levels ofwater in the reaction mixture will lead to a significant population ofhigher molecular weight chains in the final polymer compositions. It isalso known that previous classes of catalysts used for epoxide CO₂copolymerizations such as those based on zinc carboxylates producealiphatic polycarbonates having broad molecular weight distributions(i.e. high polydispersity indices PDIs) and/or relatively highproportions of ether linkages.

Therefore, polymer compositions made with the inventive catalystsdescribed herein are different in key respects from any aliphaticpolycarbonate compositions previously described. Without being bound bytheory, or thereby limiting the scope of this invention, it is believedthe unique monomodal characteristics of the inventive polymercompositions are explained by a mechanism such as that shown in Scheme2.

As shown in Scheme 2, using the inventive catalysts, the two populationsof polymer have the same degree of polymerization and thereforeessentially identical Mn. This leads to the observed monomodal molecularweight distribution.

FIGS. 9a and 9b show GPC traces for samples of poly(propylene carbonate)made with a catalyst of the present invention having a carbonatecounterion. FIG. 9c shows a similar PPC composition made with anotherwise identical catalyst that had a nitrate initiator. The GPC ofthe polymer composition from the inventive carbonate catalyst issubstantially monomodal, while the polymer composition from the nitratecatalyst shows the bimodal distribution typical of prior art polymercompositions.

The polymers of the present invention are useful since a bimodal Mndistribution in a polymer composition can be undesirable. For example,it is known that differences in the molecular weight distribution ofpolymers can affect their processing characteristics and physicalproperties. Furthermore, since it is impractical to precisely controlthe water content of reaction mixtures between polymerization batches ina commercial process, it is very difficult to make aliphaticpolycarbonate products with consistent molecular weight profiles frombatch to batch. This variability is not desirable since the differencesin the molecular weight distributions between batches may lead tocorresponding inconsistencies in processing characteristics or productperformance.

It should be noted that, because of the way the polydispersity isdefined, some prior art polymers with bimodal molecular weightdistributions still have very low polydisperisty indices (PDIs). It isunderstood in the art that low polydispersity does not equate to amono-modal molecular weight distribution. It is also noted that while itis possible to separate monodisperse polymer fractions using methodssuch as gel permeation chromatography (GPC), this is only practical forsmall analytical samples and has no utility at commercial scale.Nonetheless, in certain embodiments, the inventive polymer compositionsof the present invention are further characterized in that they have notbeen fractionated or otherwise treated in a post-polymerization step tosubstantially change their molecular weight distribution.

Therefore, in certain embodiments, the present invention providesaliphatic polycarbonate compositions characterized in that they havenarrow and monomodal molecular weight distributions.

In certain embodiments, the narrow molecular weight distribution is suchthat the PDI of the composition is less than 1.7. In certainembodiments, the PDI of the composition is less than 1.6, less than 1.5,less than 1.4, less than 1.3, less than 1.25, less than 1.2, less than1.15, or less than 1.1.

In certain embodiments, the inventive aliphatic polycarbonatecompositions of the present invention are characterized in that theyconform to the PDI limitations just described and are also characterizedin that, when the Mn is measure by GPC, at least 90% of the polymerchains belong to a single molecular weight population. In certainembodiments, aliphatic polycarbonate compositions of the presentinvention are characterized in that at least 92.5%, at least 95%, atleast 95%, at least 97%, at least 97.5%, at least 98%, at least 98.5%,at least 99%, or at least 99.5% of the polymer chains belong to a singlemolecular weight population. In certain embodiments, essentially all ofthe chains belong to a single molecular weight population.

In certain embodiments, the inventive aliphatic polycarbonatecompositions of the present invention are characterized in that theyconform to the PDI limitations just described and are also characterizedin that, when the Mn is measure by GPC, less than 10% of the polymerbelongs to a lower molecular weight population with an Mn ofapproximately one half of the molecular weight of the predominatemolecular weight population. In certain embodiments, less than 8%, lessthan 7.5%, less than 6%, less than 5%, less than 4%, less than 3%, lessthan 2% or less than 1% of the polymer belongs to a lower molecularweight population with an Mn of approximately one half of the molecularweight of the predominate molecular weight population.

In certain embodiments, the inventive aliphatic polycarbonatecompositions are further characterized in that they have high molecularweights. In certain embodiments, the aliphatic polycarbonatecompositions have an Mn above about 40,000 g/mol. In certainembodiments, the aliphatic polycarbonate compositions have an Mn of atleast 50,000 g/mol, at least 75,000 g/mol, at least 100,000 g/mol, atleast 125,000 g/mol, at least 150,000 g/mol, at least 175,000 g/mol, atleast 200,000 g/mol, or at least at least 250,000 g/mol.

In certain embodiments, the inventive aliphatic polycarbonatecompositions comprise copolymers of CO₂ and one or more epoxides whereinthe PDI less than 1.5, less than 1.3, less than 1.2 or less than 1.1 andthe Mn is above 50,000 g/mol, above 75,000 g/mol, above 100,000 g/mol,or above 150,000 g/mol; characterized in that a GPC of the compositionshows a unimodal molecular weight distribution. In certain embodiments,the unimodal molecular weight distribution is characterized in that morethan 95%, more than 98%, or more than 99% of the polymer chains belongto a single molecular weight population. In certain embodiments, theepoxide CO₂ copolymers are further characterized in that at least 95% ofthe linkages between adjacent enchained epoxides are carbonate linkages.In certain embodiments, such aliphatic polycarbonate compositions arefurther characterized in that, if there is a minor secondary populationof polymer chains belonging to a different molecular weight populationpresent, the polymer chains in the minor population have a lower Mn thanthe predominate molecular weight population. In certain embodiments, thelower Mn population has an Mn approximately one half the Mn of thepredominate molecular weight population.

In certain embodiments, the inventive aliphatic polycarbonates comprisepoly(propylene carbonate) (PPC) wherein the PDI less than 1.5, less than1.3, less than 1.2 or less than 1.1 and the Mn is above 50,000 g/mol,above 75,000 g/mol, above 100,000 g/mol, or above 150,000 g/mol;characterized in that a GPC of the composition shows a unimodalmolecular weight distribution. In certain embodiments, the unimodalmolecular weight distribution is characterized in that more than 95%,more than 98%, or more than 99% of the polymer chains belong to a singlemolecular weight population. In certain embodiments, the PPCcompositions are further characterized in that at least 95% of thelinkages between adjacent enchained propylene oxide units are carbonatelinkages. In certain embodiments, such PPC compositions are furthercharacterized in that, if there is a minor secondary population ofpolymer chains belonging to a different molecular weight populationpresent, the polymer chains in the minor population have a lower Mn thanthe predominate molecular weight population. In certain embodiments, thelower Mn population has an Mn approximately one half the Mn of thepredominate molecular weight population.

In certain embodiments, the inventive aliphatic polycarbonates comprisepoly(ethylene carbonate) (PEC) wherein the PDI is less than 1.5, lessthan 1.3, less than 1.2 or less than 1.1 and the Mn is above 50,000g/mol, above 75,000 g/mol, above 100,000 g/mol, or above 150,000 g/mol;characterized in that a GPC of the composition shows a unimodalmolecular weight distribution. In certain embodiments, the unimodalmolecular weight distribution is characterized in that more than 90%,more than 95%, more than 98%, or more than 99% of the polymer chainsbelong to a single molecular weight population. In certain embodiments,the PEC compositions are further characterized in that at least 95% ofthe linkages between adjacent enchained propylene oxide units arecarbonate linkages. In certain embodiments, such PEC compositions arefurther characterized in that, if there is a minor secondary populationof polymer chains belonging to a different molecular weight population,the polymer chains in the minor population have a lower Mn than thepredominate molecular weight population. In certain embodiments, thelower Mn population has an Mn approximately one half the Mn of thepredominate molecular weight population.

In certain embodiments, the inventive aliphatic polycarbonates comprisepoly(butylene carbonate) (PBC) wherein the PDI less than 1.5, less than1.3, less than 1.2 or less than 1.1 and the Mn is above 50,000 g/mol,above 75,000 g/mol, above 100,000 g/mol, or above 150,000 g/mol;characterized in that a GPC of the composition shows a unimodalmolecular weight distribution. In certain embodiments, the unimodalmolecular weight distribution is characterized in that more than 90%,more than 95%, more than 98%, or more than 99% of the polymer chainsbelong to a single molecular weight population. In certain embodiments,such PBC compositions are further characterized in that, if there is aminor secondary population of polymer chains belonging to a differentmolecular weight population, the polymer chains in the minor populationhave a lower Mn than the predominate molecular weight population. Incertain embodiments, the lower Mn population has an Mn approximately onehalf the Mn of the predominate molecular weight population.

Certain catalysts of the present invention provide novel polymerproducts that have narrow and unimodal molecular weight distributions.For example, when a catalyst with only dianionic counterions asdescribed above is used for epoxide CO₂ copolymerization, the polymercompositions arising from the copolymerization of CO₂ and epoxides usingthe catalyst exhibit only one peak in the GPC. Therefore, in anotheraspect, the present invention comprises a method for the synthesis ofaliphatic polycarbonates having narrow and monomodal molecular weightdistributions. In certain embodiments, the methods comprise the step ofcontacting a mixture of one or more epoxides and CO₂ with any of themetal complexes described hereinabove characterized in that theycomprise dianionic counterions.

EXAMPLES Example 1 Preparation of Compound N, a cobalt(III)salen Complexwith an Oxalate Counterion

A sample of the nitrate complex M (1 g, 1.2 mmol) was dissolved inisopropanol (7 mL) and isopropyl acetate (7 mL). A solution of sodiumoxalate (7.4 g, 55 mmol) in water (80 mL) was prepared. The solution ofnitrate complex M was washed with the aqueous oxalate solution (2×10 mL)and then water (2×10 mL). The organic solution was stripped to a minimalvolume and diluted with isopropyl ether. The green precipitate thatformed was collected by filtration to provide oxalate complex N (0.67 g,68%) as a mixture of two isomers observed by NMR in approximately a 10:1ratio in d₆-DMSO. ¹H NMR (400 MHz, d₆-DMSO): δ 1.0-1.25 (m, 27 H),1.25-2.40 (m, 14 H), 2.7-3.2 (m, 13 H), 3.94 (t, J=11 Hz, 1H), 6.88 (d,J=2.4 Hz, 0.1 H), 6.95 (d, J=2.5 Hz, 0.9 H), 7.08 (d, J=2.5 Hz, 0.9 H),7.12 (d, J=2.5 Hz, 0.9 H), 7.14 (t, J=2.5 Hz, 0.2 H), 7.19 (d, J=2.6 Hz,1 H), 7.45 (s, 0.9 H), 7.47 (s, 0.1 H), 7.74 (broad s, 1H), 7.90 (s, 0.1H), 7.91 (s, 0.9 H). The UV-vis absorption spectrum of this compoundshows absorption maxima centered at 200, 232, 263, and 406 nm.

Example 2 Preparation of Compound O, a cobalt(III)salen Complex with aMalonate Counterion

A sample of the nitrate complex M (1 g, 1.2 mmol) was dissolved inisopropanol (7 mL) and isopropyl acetate (7 mL). A solution of sodiummalonate (8.15 g, 55 mmol) in water (50 mL) was prepared. The solutionof nitrate complex M was washed with the aqueous oxalate solution (2×10mL) and then water (2×10 mL). The organic solution was stripped todryness and the resulting solid was re-dissolved in a minimal volume ofisopropanol and methanol. Isopropyl ether was added and the greenprecipitate that formed was collected by filtration to provide malonatecomplex O (0.57 g, 57%) as a mixture of two isomers observed by NMR inapproximately a 6:1 ratio in d₆-DMSO. ¹H NMR (300 MHz, d₆-DMSO): δ1.17-1.40 (m, 27 H), 1.40-2.05 (m, 14 H), 2.8-3.6 (m, 15 H), 4.48 (t,J=10 Hz, 1H), 6.84 (d, J=2.5 Hz, 0.15 H), 6.90 (d, J=2.5 Hz, 0.85 H),7.09-7.22 (m, 3H), 7.33 (s, 0.85 H), 7.38 (s, 0.15 H), 7.68 (broad s,1H), 7.72 (s, 0.15 H), 7.74 (s, 0.85 H). The UV-vis absorption spectrumof this compound shows absorption maxima centered at 199, 235, 264, and402 nm.

Example 3 Preparation of Compound Q, a cobalt(III)salen Complex with aCarbonate Counterion

A toluene and isopropyl alcohol solution (30 mL each) of the salencobalt(III) complex M′ (10.3 mmol, X=OAc, Cl, Br) was washed withsaturated sodium bicarbonate (1×50 mL, 1×25 mL). The dark solution wasthen stripped (−27 mL solvent) and polish filtered; approximately 20 mLisopropanol was used in the transfer and washing of the filter cake.Another 40 mL of solvent was stripped and the concentrated solution wasdiluted with isopropyl acetate (60 mL). A green precipitate formed andwas collected by filtration. After oven drying at 40° C. (100 mBar)overnight, the salen cobalt(III) carbonate complex was obtained as agreen powder in 69% yield (5.75 g). Proton NMR shows a mixture of twoisomers in approximately a 2:1 ratio in d₆-DMSO. ¹H NMR (400 MHz,d₆-DMSO): δ 1.16-1.33 (m, 27 H), 1.34-2.43 (m, 14 H), 2.56-3.3 (m, 13H), 3.74 (m, 1H), 6.87 (d, J=2.5 Hz, 0.35 H), 6.94 (d, J=2.5 Hz, 0.65H), 7.03-7.20 (m, 3H), 7.42 (s, 0.65 H), 7.46 (s, 0.35 H), 7.78 (broads, 1H), 7.96 (s, 0.35 H), 7.98 (s, 0.65 H). The UV-vis absorptionspectrum of this compound shows absorption maxima centered at 199, 238,263, and 410 nm.

Example 4 Preparation of Compound R, a cobalt(III)salen Complex with aCarbonate Counterion

A propanol and butyl acetate solution (50 mL each) of the salencobalt(III) complex L (17.2 mmol, X=OAc, Cl, Br) was washed withsaturated sodium bicarbonate (1×100 mL, 1×50 mL). The dark solution wasthen stripped (−70 mL solvent). Approximately 10 mL isopropanol wasadded along with more butyl acetate (50 mL). The dark solution wasstripped further and then diluted with MTBE (120 mL). The resultingsuspension was cooled to ca. 10° C. and the product R was collected byfiltration. The filter cake was washed with MTBE (2×75 mL) and thendried overnight in a vacuum oven at 30° C. (100 mBar). The salencobalt(III) carbonate complex R was obtained as a green powder in 68%yield (9.4 g) after correcting for volatiles. Proton NMR shows a mixtureof two isomers in approximately a 2:1 ratio. ¹H NMR (400 MHz, d₆-DMSO):δ 1.16-1.37 (m, 27 H), 1.37-1.95 (m, 12 H), 2.20-2.42 (m, 2H), 2.56 (s,1H), 2.59 (s, 2H), 2.77-3.36 (m, 13 H), 3.79 (m, 1H), 6.89 (d, J=2.5 Hz,0.35 H), 6.95 (d, J=2.5 Hz, 0.65 H), 7.05-7.15 (m, 3H), 7.36 (s, 0.65H), 7.44 (s, 0.35 H), 8.03 (s, 0.35 H), 8.04 (s, 0.65 H). NOV-067-235. R(Gen2b CO3): The UV-vis absorption spectrum of this compound showsabsorption maxima centered at 199, 235, 265, and 416 nm.

Example 5 Preparation of Compound T, a chromium(III)salen Complex withan Oxalate Counterion

A sample of the nitrate complex S (1.2 mmol) is dissolved in isopropanol(7 mL) and isopropyl acetate (7 mL). A solution of sodium oxalate (7.4g, 55 mmol) in water (80 mL) is prepared. The solution of nitratecomplex S is washed with the aqueous oxalate solution (2×10 mL) and thenwater (2×10 mL). The organic solution is stripped to a minimal volumeand diluted with isopropyl ether. The precipitate formed is collected byfiltration to provide oxalate complex T as a green solid.

Example 6 Preparation of Compound U, a chromium(III)salen Complex with aMalonate Counterion

A sample of the nitrate complex S (1.2 mmol) is dissolved in isopropanol(7 mL) and isopropyl acetate (7 mL). A solution of sodium malonate (8.15g, 55 mmol) in water (50 mL) is prepared. The solution of nitratecomplex S is washed with the aqueous oxalate solution (2×10 mL) and thenwater (2×10 mL). The organic solution is stripped to dryness and theresulting solid is re-dissolved in a minimal volume of isopropanol andmethanol. Isopropyl ether is added and the precipitate formed iscollected by filtration to provide malonate complex U.

Example 7 Preparation of Compound Q, a chromium(III)salen Complex with aCarbonate Counterion

A toluene and isopropyl alcohol solution (30 mL each) of the salenchromium(III) complex S′ (10.3 mmol, X=OAc, Cl, Br) is washed withsaturated sodium bicarbonate (1×50 mL, 1×25 mL). The dark solution isthen stripped and polish filtered; isopropanol is used in the transferand washing of the filter cake. Another 40 mL of solvent is stripped andthe concentrated solution is diluted with isopropyl acetate (60 mL). Aprecipitate forms and is collected by filtration. After oven drying at40° C. (100 mBar) overnight, the salen chromium(III) carbonate complex Vis obtained.

Example 8 Preparation of Compound Y, a chromium(III)salen Complex with aCarbonate Counterion

A propanol and butyl acetate solution (50 mL each) of the salenchromium(III) complex W (17.2 mmol, X=OAc, Cl, Br) is washed withsaturated sodium bicarbonate (1×100 mL, 1×50 mL). The solution is thenstripped (−70 mL solvent). Approximately 10 mL isopropanol is addedalong with more butyl acetate (50 mL). The solution is stripped furtherand then diluted with MTBE (120 mL). The resulting suspension is cooledto ca. 10° C. and the product Y is collected by filtration. The filtercake is washed with MTBE (2×75 mL) and then dried overnight in a vacuumoven at 30° C. (100 mBar). The salen chromium(III) carbonate complex Yis obtained as a powder.

OTHER EMBODIMENTS

The foregoing has been a description of certain non-limiting embodimentsof the invention. Accordingly, it is to be understood that theembodiments of the invention herein described are merely illustrative ofthe application of the principles of the invention. Reference herein todetails of the illustrated embodiments is not intended to limit thescope of the claims, which themselves recite those features regarded asessential to the invention.

APPENDIX A

This appendix describes in more detail the compositions and connectivityof the tethered activating groups mentioned above.

In some embodiments, the moiety

(Z)_(m) in compounds described hereinabove, (also referred to as “anactivating functional group”) is selected from those described below inthis appendix. In certain embodiments, an activating functional group isselected from the group consisting of neutral nitrogen-containingfunctional groups, cationic moieties, phosphorous-containing functionalgroups, and combinations of two or more of these.

A.1. Tether Moieties

In certain embodiments, each activating moiety

(Z)_(m) comprises a tether “

” coupled to at least one activating functional group Z as describedabove, with m denoting the number of activating functional groupspresent on a single Z-linker moiety.

In some embodiments, there is one or more activating moieties

(Z)_(m) tethered to a given metal complex; similarly, each activatingmoiety itself may contain more than one activating functional group Z.In certain embodiments, each activating moiety contains only oneactivating functional group (i.e. m=1). In some embodiments, eachactivating moiety contains more than one activating functional groups(i.e. m>1). In certain embodiments, an activating moiety contains twoactivating functional groups (i.e. m=2). In certain embodiments, anactivating moiety contains three activating functional groups (i.e.m=3). In certain embodiments, an activating moiety contains fouractivating functional groups (i.e. m=4). In certain embodiments wheremore than one activating functional group is present on an activatingmoiety, the activating functional groups are the same. In someembodiments where more than one activating functional group is presenton an activating moiety, two or more of the activating functional groupsare different.

In certain embodiments, each tether (or “Z-linker”) moiety

contains 1-30 atoms including at least one carbon atom, and optionallyone or more atoms selected from the group consisting of N, O, S, Si, B,and P.

In certain embodiments, a Z-linker is a bivalent, optionally substitutedC₂₋₃₀ aliphatic group wherein one or more carbons are optionally andindependently replaced by -Cy-, —NR—, —N(R)C(O)—, —C(O)N(R)—, —O—,—C(O)—, —OC(O)—, —C(O)O—, —S—, —SO—, —SO₂—, —C(═S)—, —C(═NR)—, or —N═N—,wherein:

-   -   each -Cy- is independently an optionally substituted 5- to        8-membered bivalent, saturated, partially unsaturated, or aryl        ring having 0-4 heteroatoms independently selected from        nitrogen, oxygen, or sulfur, or an optionally substituted 8-10        membered bivalent saturated, partially unsaturated, or aryl        bicyclic ring having 0-5 heteroatoms independently selected from        nitrogen, oxygen, or sulfur; and    -   R is as defined above.

In certain embodiments, a Z-linker moiety is a C₄-C₁₂ aliphatic groupsubstituted with one or more moieties selected from the group consistingof halogen, —NO₂, —CN, —SR, —S(O)R, —S(O)₂R, —NRC(O)R, —OC(O)R, —CO₂R,—NCO, —N₃, —OR⁴, —OC(O)N(R)₂, —N(R)₂, —NRC(O)R, and —NRC(O)OR, whereeach R and R⁴ is independently as defined herein and described inclasses and subclasses herein.

In certain embodiments, a Z-linker moiety is an optionally substitutedC₃-C₃₀ aliphatic group. In certain embodiments, a Z-linker is anoptionally substituted C₄₋₂₄ aliphatic group. In certain embodiments, aZ-linker moiety is an optionally substituted C₄-C₂₀ aliphatic group. Incertain embodiments, a Z-linker moiety is an optionally substitutedC₄-C₁₂ aliphatic group. In certain embodiments, a Z-linker is anoptionally substituted C₄₋₁₀ aliphatic group. In certain embodiments, aZ-linker is an optionally substituted C₄₋₈ aliphatic group. In certainembodiments, a Z-linker moiety is an optionally substituted C₄-C₆aliphatic group. In certain embodiments, a Z-linker moiety is anoptionally substituted C₆-C₁₂ aliphatic group. In certain embodiments, aZ-linker moiety is an optionally substituted C₈ aliphatic group. Incertain embodiments, a Z-linker moiety is an optionally substituted C₇aliphatic group. In certain embodiments, a Z-linker moiety is anoptionally substituted C₆ aliphatic group. In certain embodiments, aZ-linker moiety is an optionally substituted C₅ aliphatic group. Incertain embodiments, a Z-linker moiety is an optionally substituted C₄aliphatic group. In certain embodiments, a Z-linker moiety is anoptionally substituted C₃ aliphatic group. In certain embodiments, aaliphatic group in the Z-linker moiety is an optionally substitutedstraight alkyl chain. In certain embodiments, the aliphatic group is anoptionally substituted branched alkyl chain. In some embodiments, aZ-linker moiety is a C₄ to C₂₀ alkyl group having one or more methylenegroups replaced by) —C(R^(∘))₂— wherein R^(∘)is as defined above. Incertain embodiments, a Z-linker moiety consists of a bivalent aliphaticgroup having 4 to 30 carbons including one or more C₁₋₄ alkylsubstituted carbon atoms. In certain embodiments, a Z-linker moietyconsists of a bivalent aliphatic group having 4 to 30 carbons includingone or more gem-dimethyl substituted carbon atoms.

In certain embodiments, a Z-linker moiety includes one or moreoptionally substituted cyclic groups selected from the group consistingof saturated or partially unsaturated carbocyclic, aryl, heterocyclic,or heteroaryl. In certain embodiments, a Z-linker moiety consists of asubstituted cyclic group. In some embodiments a cyclic group is part ofa Z-linker, wherein one or more non-ring heteroatoms or optionallysubstituted aliphatic groups comprise other parts of the Z-linkermoiety.

In some embodiments, a Z-linker moiety is of sufficient length to allowone or more activating functional groups to be positioned near a metalatom of a metal complex. In certain embodiments, structural constraintsare built into a Z-linker moiety to control the disposition andorientation of one or more activating functional groups near a metalcenter of a metal complex. In certain embodiments, such structuralconstraints are selected from the group consisting of cyclic moieties,bicyclic moieties, bridged cyclic moieties and tricyclic moieties. Insome embodiments, such structural constraints are the result of acyclicsteric interactions. In certain embodiments, steric interactions due tosyn-pentane, gauche-butane, and/or allylic strain in a Z-linker moiety,bring about structural constraints that affect the orientation of aZ-linker and one or more activating groups. In certain embodiments,structural constraints are selected from the group consisting of cisdouble bonds, trans double bonds, cis allenes, trans allenes, and triplebonds. In some embodiments, structural constraints are selected from thegroup consisting of substituted carbons including geminallydisubstituted groups such as sprirocyclic rings, gem dimethyl groups,gem diethyl groups and gem diphenyl groups. In certain embodiments,structural constraints are selected from the group consisting ofheteroatom-containing functional groups such as sulfoxides, amides, andoximes.

In certain embodiments, Z-linker moieties are selected from the groupconsisting of:

-   -   wherein each s is independently 0-6, t is 0-4, R^(y) as defined        above and described in classes and subclasses herein, *        represents the site of attachment to a ligand, and each #        represents a site of attachment of an activating functional        group.

In some embodiments, s is 0. In some embodiments, s is 1. In someembodiments, s is 2. In some embodiments, s is 3. In some embodiments, sis 4. In some embodiments, s is 5. In some embodiments, s is 6.

In some embodiments, t is 1. In some embodiments, t is 2. In someembodiments, t is 3. In some embodiments, t is 4.

A.2. Neutral Nitrogen-Containing Activating Groups

In some embodiments, one or more tethered activating functional groups(i.e., Z) on provided metal complexes are neutral nitrogen-containingmoieties. In certain embodiments, one or more Z group is independently aneutral functional group selected from the group consisting of amines,phosphines, guanidines, bis-guanidines, amidines, andnitrogen-containing heterocycles.

In some embodiments, such Z moieties are selected from one or more ofthe structures in Table Z-1:

TABLE Z-1

or a combination of two or more of these,

wherein:

-   -   each R¹ and R² is independently hydrogen or an optionally        substituted radical selected from the group consisting of C₁₋₂₀        aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated        or partially unsaturated monocyclic carbocycle; a 7- to        14-membered saturated or partially unsaturated polycyclic        carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having        1-4 heteroatoms independently selected from nitrogen, oxygen, or        sulfur; an 8- to 14-membered polycyclic heteroaryl ring having        1-5 heteroatoms independently selected from nitrogen, oxygen, or        sulfur; a 3- to 8-membered saturated or partially unsaturated        monocyclic heterocyclic ring having 1-3 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; a 6- to        14-membered saturated or partially unsaturated polycyclic        heterocycle having 1-5 heteroatoms independently selected from        nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered        polycyclic aryl ring; wherein R¹ and R² can be taken together        with intervening atoms to form one or more optionally        substituted rings optionally containing one or more additional        heteroatoms;    -   each R³ is independently hydrogen or an optionally substituted        radical selected from the group consisting of C₁₋₂₀ aliphatic;        C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially        unsaturated monocyclic carbocycle; a 7- to 14-membered saturated        or partially unsaturated polycyclic carbocycle; a 5- to        6-membered monocyclic heteroaryl ring having 1-4 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; an 8-        to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; a 3- to        8-membered saturated or partially unsaturated monocyclic        heterocyclic ring having 1-3 heteroatoms independently selected        from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated        or partially unsaturated polycyclic heterocycle having 1-5        heteroatoms independently selected from nitrogen, oxygen, or        sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring;        wherein an R³ group can be taken with an R¹ or R² group to form        one or more optionally substituted rings; and    -   each R⁴ is independently hydrogen, a hydroxyl protecting group,        or an optionally substituted radical selected from the group        consisting of C₁₋₂₀ acyl; C₁₋₂₀ aliphatic; C₁₋₂₀        heteroaliphatic; a 3- to 8-membered saturated or partially        unsaturated monocyclic carbocycle; a 7- to 14-membered saturated        or partially unsaturated polycyclic carbocycle; a 5- to        6-membered monocyclic heteroaryl ring having 1-4 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; an 8-        to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; a 3- to        8-membered saturated or partially unsaturated monocyclic        heterocyclic ring having 1-3 heteroatoms independently selected        from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated        or partially unsaturated polycyclic heterocycle having 1-5        heteroatoms independently selected from nitrogen, oxygen, or        sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring.

In certain embodiments, each R¹ group is the same. In other embodiments,R¹ groups are different. In certain embodiments, R¹ is hydrogen. In someembodiments, R¹ is an optionally substituted radical selected from thegroup consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic, 5- to14-membered heteroaryl, phenyl, 8- to 10-membered aryl and 3- to7-membered heterocyclic. In some embodiments, R¹ is an optionallysubstituted radical selected from the group consisting of a 3- to8-membered saturated or partially unsaturated monocyclic carbocycle; a7- to 14-membered saturated or partially unsaturated polycycliccarbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur; an8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to14-membered polycyclic aryl ring.

In certain embodiments, R¹ is an optionally substituted radical selectedfrom the group consisting of C₁₋₁₂ aliphatic and C₁₋₁₂ heteroaliphatic.In some embodiments, R¹ is optionally substituted C₁₋₂₀ aliphatic. Insome embodiments, R¹ is optionally substituted C₁₋₁₂ aliphatic. In someembodiments, R¹ is optionally substituted C₁₋₆ aliphatic. In someembodiments, R¹ is optionally substituted C₁₋₂₀ heteroaliphatic. In someembodiments, R¹ is optionally substituted C₁₋₁₂ heteroaliphatic. In someembodiments, R¹ is optionally substituted phenyl. In some embodiments,R¹ is optionally substituted 8- to 10-membered aryl. In someembodiments, R¹ is an optionally substituted 5- to 6-membered heteroarylgroup. In some embodiments, R¹ is an optionally substituted 8- to14-membered polycyclic heteroaryl group. In some embodiments, R¹ isoptionally substituted 3- to 8-membered heterocyclic.

In certain embodiments, each R¹ is independently hydrogen, methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionallysubstituted phenyl, or optionally substituted benzyl. In certainembodiments, R¹ is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, phenyl or benzyl. In some embodiments, R¹ is butyl. In someembodiments, R¹ is isopropyl. In some embodiments, R¹ is neopentyl. Insome embodiments, R¹ is perfluoro. In some embodiments, R¹ is —CF₂CF₃.In some embodiments, R¹ is phenyl. In some embodiments, R¹ is benzyl.

In certain embodiments, each R² group is the same. In other embodiments,R² groups are different. In certain embodiments, R² is hydrogen. In someembodiments, R² is an optionally substituted radical selected from thegroup consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic, 5- to14-membered heteroaryl, phenyl, 8- to 10-membered aryl and 3- to7-membered heterocyclic. In some embodiments, R² is an optionallysubstituted radical selected from the group consisting of a 3- to8-membered saturated or partially unsaturated monocyclic carbocycle; a7- to 14-membered saturated or partially unsaturated polycycliccarbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur; an8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to14-membered polycyclic aryl ring.

In certain embodiments, R² is an optionally substituted radical selectedfrom the group consisting of C₁₋₁₂ aliphatic and C₁₋₁₂ heteroaliphatic.In some embodiments, R² is optionally substituted C₁₋₂₀ aliphatic. Insome embodiments, R² is optionally substituted C₁₋₁₂ aliphatic. In someembodiments, R² is optionally substituted C₁₋₆ aliphatic. In someembodiments, R² is optionally substituted C₁₋₂₀ heteroaliphatic. In someembodiments, R² is optionally substituted C₁₋₁₂ heteroaliphatic. In someembodiments, R² is optionally substituted phenyl. In some embodiments,R² is optionally substituted 8- to 10-membered aryl. In someembodiments, R² is an optionally substituted 5- to 6-membered heteroarylgroup. In some embodiments, R² is an optionally substituted 8- to14-membered polycyclic heteroaryl group. In some embodiments, R² isoptionally substituted 3- to 8-membered heterocyclic.

In certain embodiments, each R² is independently hydrogen, methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionallysubstituted phenyl, or optionally substituted benzyl. In certainembodiments, R² is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, phenyl or benzyl. In some embodiments, R² is butyl. In someembodiments, R² is isopropyl. In some embodiments, R² is neopentyl. Insome embodiments, R² is perfluoro. In some embodiments, R² is —CF₂CF₃.In some embodiments, R² is phenyl. In some embodiments, R² is benzyl.

In certain embodiments, each R¹ and R² are hydrogen. In someembodiments, each R¹ is hydrogen each and each R² is other thanhydrogen. In some embodiments, each R² is hydrogen each and each R¹ isother than hydrogen.

In certain embodiments, R¹ and R² are both methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, phenyl or benzyl. In some embodiments, R¹and R² are each butyl. In some embodiments, R¹ and R² are eachisopropyl. In some embodiments, R¹ and R² are each perfluoro. In someembodiments, R¹ and R² are —CF₂CF₃. In some embodiments, R¹ and R² areeach phenyl. In some embodiments, R¹ and R² are each benzyl.

In some embodiments, R¹ and R² are taken together with intervening atomsto form one or more optionally substituted carbocyclic, heterocyclic,aryl, or heteroaryl rings. In certain embodiments, R¹ and R² are takentogether to form a ring fragment selected from the group consisting of:—C(R^(y))₂—, —C(R^(y))₂C(R^(y))₂—, —C(R^(y))₂C(R^(y))₂C(R^(y))₂—,—C(R^(y))₂OC(R^(y))₂—, and —C(R^(y))₂NR^(y)C(R^(y))₂—, wherein R^(y) isas defined above. In certain embodiments, R¹ and R² are taken togetherto form a ring fragment selected from the group consisting of: —CH₂—,—CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂OCH₂—, and —CH₂NR^(y)CH₂—. In someembodiments, R¹ and R² are taken together to form an unsaturated linkermoiety optionally containing one or more additional heteroatoms. In someembodiments, the resulting nitrogen-containing ring is partiallyunsaturated. In certain embodiments, the resulting nitrogen-containingring comprises a fused polycyclic heterocycle.

In certain embodiments, R³ is H. In certain embodiments, R³ isoptionally C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic, 5- to 14-memberedheteroaryl, phenyl, 8- to 10-membered aryl or 3- to 7-memberedheterocyclic. In some embodiments, R³ is an optionally substitutedradical selected from the group consisting of a 3- to 8-memberedsaturated or partially unsaturated monocyclic carbocycle; a 7- to14-membered saturated or partially unsaturated polycyclic carbocycle; a5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8- to14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to14-membered polycyclic aryl ring. In certain embodiments, R³ isoptionally substituted C₁₋₁₂ aliphatic. In some embodiments, R³ isoptionally substituted C₁₋₆ aliphatic. In certain embodiments, R³ isoptionally substituted phenyl.

In certain embodiments, R³ is methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, phenyl or benzyl. In some embodiments, R³ isbutyl. In some embodiments, R³ is isopropyl. In some embodiments, R³ isperfluoro. In some embodiments, R³ is —CF₂CF₃.

In some embodiments, one or more R¹ or R² groups are taken together withR³ and intervening atoms to form an optionally substituted heterocyclicor heteroaryl ring. In certain embodiments, R¹ and R³ are taken togetherto form an optionally substituted 5- or 6-membered ring. In someembodiments, R² and R³ are taken together to form an optionallysubstituted 5- or 6-membered ring optionally containing one or moreadditional heteroatoms. In some embodiments, R¹, R² and R³ are takentogether to form an optionally substituted fused ring system. In someembodiments, such rings formed by combinations of any of R¹, R² and R³are partially unsaturated or aromatic.

In certain embodiments, R⁴ is hydrogen. In some embodiments, R⁴ is anoptionally substituted radical selected from the group consisting ofC₁₋₁₂ aliphatic, phenyl, 8- to 10-membered aryl, and 3- to 8-memberedheterocyclic. In certain embodiments, R⁴ is a C₁₋₁₂ aliphatic. Incertain embodiments, R⁴ is a C₁₋₆ aliphatic. In some embodiments, R⁴ isan optionally substituted 8- to 10-membered aryl group. In certainembodiments, R⁴ is optionally substituted C₁₋₁₂ acyl or in someembodiments, optionally substituted C₁₋₆ acyl. In certain embodiments,R⁴ is optionally substituted phenyl. In some embodiments, R⁴ is ahydroxyl protecting group. In some embodiments, R⁴ is a silyl protectinggroup. In some embodiments, R⁴ is methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, allyl, phenyl or benzyl.

In certain embodiments, R¹ and R⁴ are taken together with interveningatoms to form one or more optionally substituted heterocyclic orheteroaryl rings optionally containing one or more additionalheteroatoms.

In some embodiments, an activating functional group is an N-linked aminogroup:

wherein R¹ and R² are as defined above and described in classes andsubclasses herein.

In some embodiments, an N-linked amino activating functional group isselected from the group consisting of:

In some embodiments, one or more activating functional groups is anN-linked hydroxyl amine derivative:

wherein R¹ and R⁴ are as defined above and described in classes andsubclasses herein.

In certain embodiments, one or more N-linked hydroxyl amine activatingfunctional groups are selected from the group consisting of:

In some embodiments, an activating functional group in a provided metalcomplex is an amidine. In certain embodiments, such amidine activatingfunctional groups are selected from:

wherein each of R¹, R², and R³ is as defined above and described inclasses and subclasses herein.

In certain embodiments, an activating functional group is an N-linkedamidine:

wherein each of R¹, R², and R³ is as defined above and described inclasses and subclasses herein. In certain embodiments, such N-linkedamidine groups are selected from the group consisting of:

In certain embodiments, activating functional groups are amidinemoieties linked through the imine nitrogen:

wherein each of R¹, R², and R³ is as defined above and described inclasses and subclasses herein. In certain embodiments, such imine-linkedamidine activating functional groups are selected from the groupconsisting of:

In certain embodiments, activating functional groups are amidinemoieties linked through a carbon atom:

wherein each of R¹, R², and R³ is as defined above and described inclasses and subclasses herein. In certain embodiments, suchcarbon-linked amidine activating groups are selected from the groupconsisting of:

In some embodiments, one or more activating functional groups is acarbamate. In certain embodiments, a carbamate is N-linked:

wherein each of R¹ and R² is as defined above and described in classesand subclasses herein. In some embodiments, a carbamate is O-linked:

wherein each of R¹ and R² is as defined above and described in classesand subclasses herein.

In some embodiments, R² is selected from the group consisting of:methyl, t-butyl, t-amyl, benzyl, adamantyl, allyl,4-methoxycarbonylphenyl, 2-(methylsulfonyl)ethyl,2-(4-biphenylyl)-prop-2-yl, 2-(trimethylsilyl)ethyl, 2-bromoethyl, and9-fluorenylmethyl.

In some embodiments, at least one activating functional group is aguanidine or bis-guanidine group:

wherein each R¹ and R² is as defined above and described in classes andsubclasses herein.

In some embodiments, each R¹ and R² is independently hydrogen oroptionally substituted C₁₋₂₀ aliphatic. In some embodiments, each R¹ andR² is independently hydrogen or optionally substituted C₁₋₁₀ aliphatic.In some embodiments, any two or more R¹ or R² groups are taken togetherwith intervening atoms to form one or more optionally substitutedcarbocyclic, heterocyclic, aryl, or heteroaryl rings. In certainembodiments, R¹ and R² groups are taken together to form an optionallysubstituted 5- or 6-membered ring. In some embodiments, three or more R¹and/or R² groups are taken together to form an optionally substitutedfused ring system.

In certain embodiments, where an activating functional group is aguanidine or bis guanidine moiety, it is selected from the groupconsisting of:

In some embodiments, an activating functional group is a urea:

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein.

In certain embodiments, activating functional groups are oxime orhydrazone groups:

wherein each of R¹, R², R³, and R⁴ is as defined above and described inclasses and subclasses herein.

In some embodiments, an activating functional group is an N-oxidederivative:

wherein each of R¹ and R² is as defined above and described in classesand subclasses herein.

In certain embodiments, an N-oxide activating functional group isselected from the group consisting of:

A.3. Cationic Activating Groups

In some embodiments, one or more tethered activating functional groupson provided metal complexes comprise a cationic moiety. In certainembodiments, one or more Z groups is independently a cationic functionalgroup selected from the group consisting of quaternary amines,guanidines, bis-guanidines, amidines, and nitrogen-containingheterocycles.

In some embodiments, Z moieties are selected from one or more of theselected from a structure in Table Z-2:

TABLE Z-2

or a combination of two or more of these,

-   -   wherein:    -   each of R¹, R², and R³ is independently as defined above and        described in classes and subclasses herein, both singly and in        combination;    -   R⁵ is R² or hydroxyl; wherein R¹ and R⁵ can be taken together        with intervening atoms to form one or more optionally        substituted carbocyclic, heterocyclic, aryl, or heteroaryl        rings;    -   each R⁶ and R⁷ is independently hydrogen or an optionally        substituted radical selected from the group consisting of C₁₋₂₀        aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated        or partially unsaturated monocyclic carbocycle; a 7- to        14-membered saturated or partially unsaturated polycyclic        carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having        1-4 heteroatoms independently selected from nitrogen, oxygen, or        sulfur; an 8- to 14-membered polycyclic heteroaryl ring having        1-5 heteroatoms independently selected from nitrogen, oxygen, or        sulfur; a 3- to 8-membered saturated or partially unsaturated        monocyclic heterocyclic ring having 1-3 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; a 6- to        14-membered saturated or partially unsaturated polycyclic        heterocycle having 1-5 heteroatoms independently selected from        nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered        polycyclic aryl ring; wherein R⁶ and R⁷ can be taken together        with intervening atoms to form one or more optionally        substituted rings optionally containing one or more heteroatoms,        and an R⁶ and R⁷ group can be taken with an R¹ or R² group to        form one or more optionally substituted rings;    -   each occurrence of R⁸ is independently selected from the group        consisting of: halogen, —NO₂, —CN, —SR^(y), —S(O)R^(y),        —S(O)₂R^(y), —NR^(y)C(O)R^(y), —OC(O)R^(y), —CO₂R^(y), —NCO,        —N₃, —OR⁷, —OC(O)N(R^(y))₂, —N(R^(y))₂, —NR^(y)C(O)R^(y),        —NR^(y)C(O)OR^(y); or an optionally substituted radical selected        from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀        heteroaliphatic; a 3- to 8-membered saturated or partially        unsaturated monocyclic carbocycle; a 7- to 14-membered saturated        or partially unsaturated polycyclic carbocycle; a 5- to        6-membered monocyclic heteroaryl ring having 1-4 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; an 8-        to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms        independently selected from nitrogen, oxygen, or sulfur; a 3- to        8-membered saturated or partially unsaturated monocyclic        heterocyclic ring having 1-3 heteroatoms independently selected        from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated        or partially unsaturated polycyclic heterocycle having 1-5        heteroatoms independently selected from nitrogen, oxygen, or        sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring;        wherein each R^(y) is independently as defined above and        described in classes and subclasses herein, and where two or        more adjacent R⁸ groups can be taken together to form an        optionally substituted saturated, partially unsaturated, or        aromatic 5- to 12-membered ring containing 0 to 4 heteroatoms;    -   Ring A is an optionally substituted, 5- to 10-membered        heteroaryl group; and    -   Ring B is an optionally substituted, 3- to 8-membered saturated        or partially unsaturated monocyclic heterocyclic ring having 0-2        heteroatoms in addition to the depicted ring nitrogen atom        independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, a cationic activating functional group is aprotonated amine:

where each of R¹ and R² is as defined above and described in classes andsubclasses herein.

In specific embodiments, a protonated amine activating functional groupis selected from the group consisting of:

In certain embodiments, an activating functional group is a guanidiniumgroup:

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein. In some embodiments, each R¹ and R² isindependently hydrogen or optionally substituted C₁₋₂₀ aliphatic. Insome embodiments, each R¹ and R² is independently hydrogen or optionallysubstituted C₁₋₁₀ aliphatic. In some embodiments, each R¹ and R² isindependently hydrogen or C₁₋₁₂ aliphatic. In some embodiments, each R¹and R² is independently hydrogen or C₁₋₂₀ heteroaliphatic. In someembodiments, each R¹ and R² is independently hydrogen or phenyl. In someembodiments, each R¹ and R² is independently hydrogen or 8- to10-membered aryl. In some embodiments, each R¹ and R² is independentlyhydrogen or 5- to 10-membered heteroaryl. In some embodiments, each R¹and R² is independently hydrogen or 3- to 7-membered heterocyclic. Insome embodiments, one or more of R¹ and R² is optionally substitutedC₁₋₁₂ aliphatic.

In some embodiments, any two or more R¹ or R² groups are taken togetherwith intervening atoms to form one or more optionally substitutedcarbocyclic, heterocyclic, aryl, or heteroaryl rings. In certainembodiments, R¹ and R² groups are taken together to form an optionallysubstituted 5- or 6-membered ring. In some embodiments, three or more R¹and/or R² groups are taken together to form an optionally substitutedfused ring system.

In certain embodiments, a R¹ and R² group are taken together withintervening atoms to form a compound selected from:

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein, and Ring G is an optionallysubstituted 5- to 7-membered saturated or partially unsaturatedheterocyclic ring.

It will be appreciated that when a guanidinium cation is depicted as

all such resonance forms are contemplated and encompassed by the presentdisclosure. For example, such groups can also be depicted as

In specific embodiments, a guanidinium activating functional group isselected from the group consisting of:

In some embodiments, an activating functional group is a sulfonium groupor an arsonium group:

wherein each of R¹, R², and R³ are as defined above and described inclasses and subclasses herein.

In specific embodiments, an arsonium activating functional group isselected from the group consisting of:

In some embodiments, an activating functional group is an optionallysubstituted nitrogen-containing heterocycle. In certain embodiments, thenitrogen-containing heterocycle is an aromatic heterocycle. In certainembodiments, the optionally substituted nitrogen-containing heterocycleis selected from the group consisting of: pyridine, imidazole,pyrrolidine, pyrazole, quinoline, thiazole, dithiazole, oxazole,triazole, pyrazolem, isoxazole, isothiazole, tetrazole, pyrazine,thiazine, and triazine.

In some embodiments, a nitrogen-containing heterocycle includes aquaternarized nitrogen atom. In certain embodiments, anitrogen-containing heterocycle includes an iminium moiety such as

In certain embodiments, the optionally substituted nitrogen-containingheterocycle is selected from the group consisting of pyridinium,imidazolium, pyrrolidinium, pyrazolium, quinolinium, thiazolium,dithiazolium, oxazolium, triazolium, isoxazolium, isothiazolium,tetrazolium, pyrazinium, thiazinium, and triazinium.

In certain embodiments, a nitrogen-containing heterocycle is linked to ametal complex via a ring nitrogen atom. In some embodiments, a ringnitrogen to which the attachment is made is thereby quaternized, and insome embodiments, linkage to a metal complex takes the place of an N—Hbond and the nitrogen atom thereby remains neutral. In certainembodiments, an optionally substituted N-linked nitrogen-containingheterocycle is a pyridinium derivative. In certain embodiments,optionally substituted N-linked nitrogen-containing heterocycle is animidazolium derivative. In certain embodiments, optionally substitutedN-linked nitrogen-containing heterocycle is a thiazolium derivative. Incertain embodiments, optionally substituted N-linked nitrogen-containingheterocycle is a pyridinium derivative.

In some embodiments, an activating functional group is

In certain embodiments, ring A is an optionally substituted, 5- to10-membered heteroaryl group. In some embodiments, Ring A is anoptionally substituted, 6-membered heteroaryl group. In someembodiments, Ring A is a ring of a fused heterocycle. In someembodiments, Ring A is an optionally substituted pyridyl group.

In some embodiments, when Z is

ring A is other than an imidazole, an oxazole, or a thiazole.

In specific embodiments, a nitrogen-containing heterocycle activatingfunctional group is selected from the group consisting of:

In certain embodiments, Ring A is a 5-membered saturated or partiallyunsaturated monocyclic heterocyclic ring. In certain embodiments, Ring Ais a 6-membered saturated or partially unsaturated heterocycle. Incertain embodiments, Ring A is a 7-membered saturated or partiallyunsaturated heterocycle. In certain embodiments, Ring A istetrahydrofuranyl, tetrahydrothienyl, pyrrolidinyl, pyrrolidonyl,piperidinyl, pyrrolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl,decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl,diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and quinuclidinyl. Insome embodiments, Ring A is piperidinyl.

In some embodiments, an activating functional group is

where each R¹, R², and R³ is independently as defined above anddescribed in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹, R², and R³ is independently as defined above anddescribed in classes and subclasses herein.

In some embodiments, an activating functional group is

, wherein each of R¹, R², R⁶, and R⁷ is as defined above and describedin classes and subclasses herein.

In certain embodiments, R⁶ and R⁷ are each independently an optionallysubstituted group selected from the group consisting of C₁₋₂₀ aliphatic;C₁₋₂₀ heteroaliphatic; phenyl, and 8-10-membered aryl. In someembodiments, R⁶ and R⁷ are each independently an optionally substitutedC₁₋₂₀ aliphatic. In some embodiments, R⁶ and R⁷ are each independentlyan optionally substituted C₁₋₂₀ heteroaliphatic having. In someembodiments, R⁶ and R⁷ are each independently an optionally substitutedphenyl or 8-10-membered aryl. In some embodiments, R⁶ and R⁷ are eachindependently an optionally substituted 5- to 10-membered heteroaryl. Insome embodiments, R⁶ and R⁷ can be taken together with intervening atomsto form one or more rings selected from the group consisting of:optionally substituted C₃-C₁₄ carbocycle, optionally substituted C₃-C₁₄heterocycle, optionally substituted C₆-C₁₀ aryl, and optionallysubstituted 5- to 10-membered heteroaryl. In some embodiments, R⁶ and R⁷are each independently an optionally substituted C₁₋₆ aliphatic. In someembodiments, each occurrence of R⁶ and R⁷ is independently methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, or benzyl. In someembodiments, each occurrence of R⁶ and R⁷ is independently perfluoro. Insome embodiments, each occurrence of R⁶ and R⁷ is independently —CF₂CF₃.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein, both singly and in combination.

In some embodiments, an activating functional group is

wherein each R¹, R², and R³ is independently as defined above anddescribed in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹, R², and R³ is independently as defined above anddescribed in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and describedin classes and subclasses herein.A.4. Phosphorus-Containing Activating Groups

In some embodiments, activating functional groups Z are phosphorouscontaining groups.

In certain embodiments, a phosphorous-containing functional group ischosen from the group consisting of: phosphines (—PR^(y) ₂); Phosphineoxides —P(O)R^(y) ₂; phosphinites P(OR⁴)R^(y) ₂; phosphonitesP(OR⁴)₂R^(y); phosphites P(OR⁴)₃; phosphinates OP(OR⁴)R^(y) ₂;phosphonates; OP(OR⁴)₂R^(y); phosphates —OP(OR⁴)₃; phosphonium salts([—PR^(y) ₃]⁺) where a phosphorous-containing functional group may belinked to a metal complex through any available position (e.g. directlinkage via the phosphorous atom, or in some cases via an oxygen atom).

In certain embodiments, a phosphorous-containing functional group ischosen from the group consisting of:

or a combination of two or more of these

-   -   wherein each R¹, R², and R⁴ is as defined above and described in        classes and subclasses herein, both singly and in combination;        and where two R⁴ groups can be taken together with intervening        atoms to form an optionally substituted ring optionally        containing one or more heteroatoms, or an R⁴ group can be taken        with an R¹ or R² group to an optionally substituted carbocyclic,        heterocyclic, heteroaryl, or aryl ring.

In some embodiments, phosphorous containing functional groups includethose disclosed in The Chemistry of Organophosphorus Compounds. Volume4. Ter- and Quinquevalent Phosphorus Acids and their Derivatives. TheChemistry of Functional Group Series Edited by Frank R. Hartley(Cranfield University, Cranfield, U.K.). Wiley: New York. 1996. ISBN0-471-95706-2, the entirety of which is hereby incorporated herein byreference.

In certain embodiments, phosphorous containing functional groups havethe formula:—(V)_(b)−[(R⁹R¹⁰R¹¹P)⁺]_(n′)W^(n′−), wherein:

-   -   V is —O—, —N═, or —NR^(z)—,    -   b is 1 or 0,    -   each of R⁹, R¹⁰ and R¹¹ are independently present or absent and,        if present, are independently selected from the group consisting        of optionally substituted C₁-C₂₀ aliphatic, optionally        substituted phenyl, optionally substituted C₈-C₁₄ aryl,        optionally substituted 3- to 14-membered heterocyclic,        optionally substituted 5- to 14-membered heteroaryl, halogen,        ═O, —OR^(z), ═NR^(z), and N(R^(z))₂ where R^(z) is hydrogen, or        an optionally substituted C₁-C₂₀ aliphatic, optionally        substituted phenyl, optionally substituted 8- to 14-membered        aryl, optionally substituted 3- to 14-membered heterocyclic, or        optionally substituted 5- to 14-membered heteroaryl,    -   W is any anion, and    -   n′ is from 1 to 4, inclusive.

In some embodiments, an activating functional group is a phosphonategroup:

wherein each R¹, R², and R⁴ is independently as defined above anddescribed in classes and subclasses herein, both singly and incombination.

In specific embodiments, a phosphonate activating functional group isselected from the group consisting of:

In some embodiments, an activating functional group is a phosphonicdiamide group:

wherein each R¹, R², and R⁴ is independently as defined above anddescribed in classes and subclasses herein. In certain embodiments, eachR¹ and R² group in a phosphonic diamide is methyl.

In some embodiments, an activating functional group is a phosphinegroup:

wherein R¹, and R² are as defined above and described in classes andsubclasses herein, both singly and in combination.

In specific embodiments, a phosphine activating functional group isselected from the group consisting of:

What is claimed is:
 1. A metal salen complex comprising a salen ligandand a metal atom selected from cobalt and chromium, wherein the salenligand includes at least one tethered moiety that is either cationic, orcapable of being protonated to form a cation, characterized in that thecomplex comprises carbonate as a counterion.
 2. The metal salen complexof claim 1, wherein the metal atom comprises cobalt.
 3. The metal salencomplex of claim 1, wherein the complex has a formula:

wherein: M is the metal atom selected from cobalt or chromium, R^(1a),R^(1a′), R^(2a) R^(2a′), R^(3a), and R^(3a′) are independently a

(Z)_(m) group, hydrogen, R, halogen, —OR, —NR₂, —SR, —CN, —NO₂, —SO₂R,—SOR, —SO₂NR₂, —CNO, —NRSO₂R, —NCO, —N₃, —SiR₃, —C(O)R, —NRC(O)R,—OC(O)R, —CO₂R, —OC(O)N(R)₂, —C(O)NR₂, —NRC(O)NR—, —NRC(O)OR, or anoptionally substituted radical selected from the group consisting ofC₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; phenyl; a 3- to 8-memberedsaturated or partially unsaturated monocyclic carbocycle; a 7- to14-membered saturated, partially unsaturated or aromatic polycycliccarbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur; a3- to 8-membered monocyclic saturated or partially unsaturatedheterocyclic ring having 1-3 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 6- to 12-membered polycyclic saturated orpartially unsaturated heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; and an 8- to 10-memberedbicyclic heteroaryl ring having 1-5 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur; each R is independently hydrogen, anoptionally substituted radical selected from the group consisting of:acyl; carbamoyl; arylalkyl; phenyl; C₁₋₁₂ aliphatic; C₁₋₁₂heteroaliphatic; a 3- to 8-membered saturated or partially unsaturatedmonocyclic carbocycle; a 7- to 14-membered saturated, partiallyunsaturated or aromatic polycyclic carbocycle; a 5- to 6-memberedmonocyclic heteroaryl ring having 1-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur; a 3- to 8-membered monocyclicsaturated or partially unsaturated heterocyclic ring having 1-3heteroatoms independently selected from nitrogen, oxygen, or sulfur; andan 8- to 10-membered bicyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, sulfur, an oxygenprotecting group, or a nitrogen protecting group, or two R on the samenitrogen atom are taken with the nitrogen to form a 3- to 7-memberedheterocyclic ring; wherein any of [R^(2a′) and R^(3a′)], [R^(2a) andR^(3a)],[R ^(1a)and R^(2a)], and [R^(1a′) and R^(2a′)]may optionally betaken together with the carbon atoms to which they are attached to formone or more rings which may in turn be optionally substituted as definedabove, or substituted with one or more R groups; and R^(G) is selectedfrom the group consisting of:

where where R^(c) groups are optionally present, and if present are,independently at each occurrence a

(Z)_(m) group, halogen, —OR, —NR₂, —SR, —CN, —NO ₂, —SO₂R, —SOR,—SO₂NR₂, —CNO, —NRSO₂R, —NCO, —N₃, —SiR₃, —C(O)R, —NRC(O)R, —OC(O)R,—CO₂R, —OC(O)N(R)₂, —C(O)NR₂, —NRC(O)NR—, —NRC(O)OR; or an optionallysubstituted radical selected from the group consisting of arylalkyl;phenyl; C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-memberedsaturated or partially unsaturated monocyclic carbocycle; a 7- to14-membered saturated, partially unsaturated or aromatic polycycliccarbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur; a3- to 8-membered monocyclic saturated or partially unsaturatedheterocyclic ring having 1-3 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; and an 8- to 10-membered bicyclicheteroaryl ring having 1-5 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; where two or more R^(c) groups may be takentogether with the carbon atoms to which they are attached and anyintervening atoms to form one or more optionally substituted rings; andwhere when two R^(c) groups are attached to the same carbon atom, theymay be taken together along with the carbon atom to which they areattached to form a moiety selected from the group consisting of: a 3- to8-membered spirocyclic ring, a carbonyl, an oxime, a hydrazone, animine, and an optionally substituted alkene; R^(C′) is, independently ateach occurrence, —H, or R^(c); Y is a bivalent linker selected from thegroup consisting of: —(CR^(c′) ₂)_(q′)—; —NR—, —N(R)C(O)—, —C(O)NR—,—O—, —C(O)—, —OC(O)—, —C(R)₂—, —C(O)O—, —S—, —SO—, —SO₂—, —C(═S)—,—C(═NR)—, or —N═N—; a polyether; C₁₋₆ aliphatic; a C₃ to C₈ substitutedor unsubstituted carbocycle; and a 3- to 8-membered substituted orunsubstituted heterocycle; R^(d) groups are optionally present, and ifpresent are independently at each occurrence selected from the groupconsisting of: a

(Z)_(m) group, halogen, R, —OR, —NR₂, —SR, —CN, —NO₂, —SO₂R, —SOR,—SO₂NR₂, —CNO, —NRSO₂R, —NCO, —N₃, —SiR₃, —C(O)R, —NRC(O)R, —OC(O)R,—CO₂R, —OC(O)N(R)₂, —C(O)NR₂, —NRC(O)NR—, —NRC(O)OR, or an optionallysubstituted group selected from the group consisting of C₁₋₂₀ aliphatic;C₁₋₂₀ heteroaliphatic having 1-4 heteroatoms independently selected fromthe group consisting of nitrogen, oxygen, and sulfur; 6-10-memberedaryl; 5-10-membered heteroaryl having 1-4 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; and 4-7-membered heterocyclichaving 1-2 heteroatoms independently selected from the group consistingof nitrogen, oxygen, and sulfur; where two or more R^(d) groups may betaken together with the carbon atoms to which they are attached and anyintervening atoms to form one or more optionally substituted ringsoptionally containing one or more heteroatoms; q′ is an integer from 1to 6, inclusive; q is an integer from 0 to 5, inclusive; x is 0, 1, or2; and

(Z)_(m) represents one or more activating moieties attached to themultidentate ligand, where

is a linker moiety covalently coupled to the ligand, each Z is anactivating functional group; and m is an integer from 1 to 4, inclusive,representing the number of Z groups present on an individual linkermoiety.
 4. The metal salen complex of claim 3, wherein at least one of[R^(2a) and R^(3a)] and [R^(2a′) and R^(3a′)] are taken together to forma ring.
 5. The metal salen complex of claim 4 having the formula:

wherein: R^(4a), R^(4a′), R^(5a), R^(5a′), R^(6a), R^(6a′), R^(7a) , andR^(7a′)are each independently hydrogen, or an R^(d) group; and wherein[R^(1a) and R^(4a)], [R^(1a′) and R^(4a′)] and any two adjacent R^(4a),R^(4a′), R^(5a), R^(5a′), R^(6a), R^(6a′), R^(7a), and R^(7a′) groupscan be taken together with intervening atoms to form one or moreoptionally substituted rings.
 6. The metal salen complex of claim 5,wherein one or more of R^(1a), R^(1a′), R^(2a), R^(2a′), R^(3a), andR^(3a′) are independently a

(Z)_(m) group.
 7. The metal salen complex of claim 4, wherein the salencomplex is selected from the group consisting of:

wherein: R^(4a), R^(4a′), R^(5a), R^(5a′), R^(6a), R^(6a′), R^(7a), andR^(7a′) are each independently hydrogen, or an R^(d) group; wherein[R^(1a) and R^(4a)], [R^(1a′) and R^(4a′)] and any two adjacent R^(4a),R^(4a′), R^(5a), R^(5a′), R^(6a), R^(6a′), R^(7a), R^(7a′) groups can betaken together with intervening atoms to form one or more optionallysubstituted rings; and R′ represents one or more substituents optionallypresent on the phenyl rings and each R′ is independently selected fromthe group consisting of: R, halogen, —OR, —NR₂, —SR, —CN, —NO₂, —SO₂R,—SOR, —SO₂NR₂, —CNO, —NRSO₂R, —NCO, —N₃, —SiR₃, —C(O)R, —NRC(O)R,—OC(O)R, —CO₂R, —OC(O)N(R)₂, —C(O)NR₂, —NRC(O)NR—, —NRC(O)OR, or anoptionally substituted radical selected from the group consisting ofC₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; phenyl; a 3- to 8-memberedsaturated or partially unsaturated monocyclic carbocycle; a 7- to14-membered saturated, partially unsaturated or aromatic polycycliccarbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4heteroatoms independently selected from nitrogen, oxygen, or sulfur; a3- to 8-membered monocyclic saturated or partially unsaturatedheterocyclic ring having 1-3 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 6- to 12-membered polycyclic saturated orpartially unsaturated heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; and an 8- to 10-memberedbicyclic heteroaryl ring having 1-5 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur.
 8. The metal salen complex of claim 7,wherein Z is selected from the following:

or a combination of two or more of these, wherein: each R^(l) and R² isindependently hydrogen or an optionally substituted radical selectedfrom the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a3- to 8-membered saturated or partially unsaturated monocycliccarbocycle; a 7- to 14-membered saturated or partially unsaturatedpolycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur; a3- to 8-membered saturated or partially unsaturated monocyclicheterocyclic ring having 1-3 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; and an 8- to14-membered polycyclic aryl ring; wherein R¹ and R² can be takentogether with intervening atoms to form one or more optionallysubstituted rings optionally containing one or more additionalheteroatoms; each R³ is independently hydrogen or an optionallysubstituted radical selected from the group consisting of C₁₋₂₀aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated orpartially unsaturated monocyclic carbocycle; a 7- to 14-memberedsaturated or partially unsaturated polycyclic carbocycle; a 5- to6-membered monocyclic heteroaryl ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8- to14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; and an 8- to14-membered polycyclic aryl ring; wherein an R³ group can be taken withan R¹ or R² group to form one or more optionally substituted rings; andeach R⁴ is independently hydrogen, a hydroxyl protecting group, or anoptionally substituted radical selected from the group consisting ofC₁₋₂₀ acyl; C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-memberedsaturated or partially unsaturated monocyclic carbocycle; a 7- to14-membered saturated or partially unsaturated polycyclic carbocycle; a5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8- to14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; and an 8- to14-membered polycyclic aryl ring.
 9. The metal salen complex of claim 1,wherein the complex is selected from:


10. The metal salen complex of claim 1, wherein the complex is selectedfrom:

where X—is an anion.
 11. The metal salen complex of claim 7, wherein Zis selected from the following:

or a combination of two or more of these, wherein: X is an anion; eachR¹ and R² is independently hydrogen or an optionally substituted radicalselected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀heteroaliphatic; a 3- to 8-membered saturated or partially unsaturatedmonocyclic carbocycle; a 7- to 14-membered saturated or partiallyunsaturated polycyclic carbocycle; a 5- to 6-membered monocyclicheteroaryl ring having 1-4 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroarylring having 1-5 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturatedmonocyclic heterocyclic ring having 1-3 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturatedor partially unsaturated polycyclic heterocycle having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; phenyl; and an8- to 14-membered polycyclic aryl ring; wherein R¹ and R² can be takentogether with intervening atoms to form one or more optionallysubstituted rings optionally containing one or more additionalheteroatoms; each R³ is independently hydrogen or an optionallysubstituted radical selected from the group consisting of C₁₋₂₀aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated orpartially unsaturated monocyclic carbocycle; a 7- to 14-memberedsaturated or partially unsaturated polycyclic carbocycle; a 5- to6-membered monocyclic heteroaryl ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8- to14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; and an 8- to14-membered polycyclic aryl ring; wherein an R³ group can be taken withan R¹ or R² group to form one or more optionally substituted rings; R⁵is R² or hydroxyl; wherein R¹ and R⁵ can be taken together withintervening atoms to form one or more optionally substitutedcarbocyclic, heterocyclic, aryl, or heteroaryl rings; each R⁶ and R⁷ isindependently hydrogen or an optionally substituted radical selectedfrom the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a3- to 8-membered saturated or partially unsaturated monocycliccarbocycle; a 7- to 14-membered saturated or partially unsaturatedpolycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ringhaving 1-4 heteroatoms independently selected from nitrogen, oxygen, orsulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5heteroatoms independently selected from nitrogen, oxygen, or sulfur; a3- to 8-membered saturated or partially unsaturated monocyclicheterocyclic ring having 1-3 heteroatoms independently selected fromnitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; and an 8- to14-membered polycyclic aryl ring; wherein R⁶ and R⁷ can be takentogether with intervening atoms to form one or more optionallysubstituted rings optionally containing one or more heteroatoms, and anR⁶ and R⁷ group can be taken with an R¹ or R² group to form one or moreoptionally substituted rings; each occurrence of R⁸ is independentlyselected from: halogen, —NO₂, —CN, —NCO, —N₃; or an optionallysubstituted radical selected from the group consisting of C₁₋₂₀aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated orpartially unsaturated monocyclic carbocycle; a 7- to 14-memberedsaturated or partially unsaturated polycyclic carbocycle; a 5- to6-membered monocyclic heteroaryl ring having 1-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; an 8- to14-membered polycyclic heteroaryl ring having 1-5 heteroatomsindependently selected from nitrogen, oxygen, or sulfur; a 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 1-3 heteroatoms independently selected from nitrogen,oxygen, or sulfur; a 6- to 14-membered saturated or partiallyunsaturated polycyclic heterocycle having 1-5 heteroatoms independentlyselected from nitrogen, oxygen, or sulfur; phenyl; and an 8- to14-membered polycyclic aryl ring; where two or more adjacent R⁸ groupscan be taken together to form an optionally substituted saturated,partially unsaturated, or aromatic 5- to 12-membered ring containing 0to 4 heteroatoms; Ring A is an optionally substituted, 5- to 10-memberedheteroaryl group; and Ring B is an optionally substituted, 3- to8-membered saturated or partially unsaturated monocyclic heterocyclicring having 0-2 heteroatoms in addition to the depicted ring nitrogenatom independently selected from nitrogen, oxygen, or sulfur.